This week there were some great cross-sectional imaging cases. One of the main points was to apply the same principles of interpretation to CT and MR images, regardless of which one you are more used to seeing at your practice for a particular lesion.

9 year old female neutered German Shepherd with polyuria/polydipsia.

On post-contrast CT images, there is a large, contrast-enhancing mass involving the pituitary. The mass is slightly asymmetric with a non-contrast enhancing region on the dorsolateral right side. The primary differential diagnosis is pituitary adenoma or adenocarcinoma. Differentials that could mimic a pituitary tumor include meningioma, granular cell tumor, and lymphoma (tends to be more diffuse). Diagnosis: Pituitary mass. Note: In human literature, pituitary adenocarcinomas are only diagnosed if there is intracranial metastatic disease. Non-metastatic tumors are termed adenoma or invasive adenoma.

12 year old Boxer with vestibular signs.

Post-contrast CT images of the brain are available. There is atrophy of the temporalis muscle and digastricus muscle on the right side. There is a broad-based, contrast-enhancing area on the left side of the brain adjacent to the tympanic bulla. It is in the region of the vestibulocochlear nerve and appears to be extra-axial with a dural tail. The tympanic bulla is normal, however mineralization of the external ear canal indicates chronic otitis externa. The primary differential diagnosis is meningioma; less likely differentials include lymphoma, peripheral nerve sheath tumor, and inflammatory disease. Diagnosis: Meningioma.

3 year old QH gelding with grade 4/5 right front lameness after trauma.

On ultrasound images, the superficial digital flexor tendon is enlarged from 19-23 cm distal to the ACB. There is a hypoechoic region with irregular fiber pattern at the caudal margin which becomes normal at 27 cm distal to the ACB. There is also moderate digital sheath effusion. There is hypoechoic relaxation artifact in the inferior check ligament which may indicate rupture of the check ligament or the deep digital flexor tendon. Differential diagnoses – superficial digital flexor tendon desmitis and check ligament rupture or rupture of the deep digital flexor tendon with secondary check ligament relaxation. Recommendation: scan the pastern to evaluate the deep digital flexor. There is a large anechoic, irregular region in the deep digital flexor tendon at the level of the pastern with severe fiber disruption. The margins of the deep digital flexor is difficult to define. Diagnosis: Superficial digital flexor tendon desmitis and deep digital flexor tendon rupture.

2 year old gelding with a mass on left mandible.

CT images of the skull are available. There is an expansile mass with irregular internal mineralization associated with the right caudal mandible. There is no evidence of cortical lysis. The mass surrounds M3 and is cauding abnormal shape and eruption of M3. M2 is also surrounded by the mass but has a normal shape. The oral cavity is narrowed by the mass. The main differential diagnosis is a congenital mass of dental origin such as ameloblastoma or cementoma, odontoma, or benign tumor such as fibroma. Note: ameloblastomas are radiolucent. Diagnosis: complex ameloblastic odontoma.

7 month old Lab with left pelvic limb lameness

On radiographs of the left stifle, there is a large radiolucent area in one condyle of the femur. On the craniocaudal projection, this appears to be located in the medial portion of the lateral condyle. There is a very mild contour irregularity of the cortex. There is increased soft tissue opacity within the joint indicating effusion. Differential diagnoses include developmental disease such as osteochondrosis or bone cyst, septic arthritis and osteomyelitis, trauma, and avulsion of a cruciate ligament. Diagnosis: Avulsion of the caudal band of the cranial cruciate ligament diagnosed at arthrotomy.

11 year old Labrador with history of maxillary neoplasia and forelimb lameness

Two radiographs of the right elbow are available for review. There is irregular sclerosis of the proximal ulna with an ill-defined lucent area parallel to the humero-ulnar joint. On nuclear scintigraphy with 99m-Tc-MDP, there is intense radiopharmaceutical uptake of the proximal ulna. The muscle mass surrounding the left thoracic limb is decreased. The left elbow is normal. Differential diagnoses include metastatic neoplasia, soft tissue tumor invading bone, fungal osteomyelitis, and primary bone tumor. Comment – this production is unusual in sarcomas or carcinomas of soft tissue unless there is bone infarction. Diagnosis: peripheral primitive neuroectodermal tumor. Biopsy was attempted twice with no definitive diagnosis. There was radiographic progression with pathologic fracture 10 months later. The diagnosis was obtained post-mortem.

10 year old FS Golden Retriever with inappetance, anorexia and intermittent and mild cough.

Thoracic radiographs show increased soft tissue opacity in the ventral thorax, located cranial and ventral to the cardiac silhouette. There is a mild bronchointerstitial pattern. There is a very small amount of pleural effusion, and the edges of the soft tissue mass are angular and displacing the lung margins dorsally. Differential diagnoses include pleural or mediastinal neoplasia and inflammatory mediastinal disease (fungal, migrating foreign body). Diagnosis: Mesothelioma.

9 year old female warmblood horse with weight loss after medical colic 1 month ago

Images of the left 13th intercosal space and left ventral abdomen are presented. The stomach is visible as a hypoechoic line with hyperechoic gas in the lumen. The stomach appears enlarged and extends beyond the costochondral junctions. The wall is thickened at 1.5 cm (normal 8 mm). The spleen is being displaced caudally by the enlarged stomach. Differential diagnoses: gastric outflow obstruction, gastric impaction. Diagnosis: gastric impaction.

This episode of KCC had some unusual appearing lesions that made a logical approach to the radiographs all the more important. See if you can come up with some differential diagnoses from the description, before you look at the answers!

12 year old female neutered West Highland White Terrier with difficulty breathing.

On thoracic radiographs, there is increased soft tissue opacity in the cranial mediastinum and superimposed over the left cranial heart on the d/v projection. The right heart is enlarged and the pulmonary vessels appear small. There is a diffuse interstitial pulmonary pattern and the thorax appears hypoinflated. The soft tissue opacity associated with the cardiac silhouette is most likely the main pulmonary artery. Differential diagnoses include breed-associated pulmonary fibrosis with secondary right heart hypertophy, or less likely a cranial mediastinal mass. Diagnosis: pulmonary fibrosis with severe pulmonary hypertension. Comment: On echocardiogram, look for pulmonic regurgitation with a velocity of 2.2 m/s to diagnose pulmonary hypertension.

10 year old domestic short hair cat with chronic respiratory issues and cough.

There is increased soft tissue opacity in the cranial thorax occupying the area of the cranial lung lobes bilaterally. The soft tissue opacity is imixed with multifocal nodular mineral opacities which also extend into the aerated portions of the lung. Some of the mineral opacities have a linear pattern which may repesent an airway association. The caudal lung lobes are hyperinflated, with a severe bronchial pattern. The carina is displaced cranially by the hyperinflated caudal lung lobes. The pleural surfaces of the caudal lung lobes are rounded and retracted from the chest wall. The cardiac silhouette is obscured by the lung pathology. Differential diagnoses include inflammatory airway disease with granulomatous change, dystrophic mineralization, +/- pulmonary neoplasia. The airway obstruction is likely causing atelectasis of the cranial lung lobes, and there appears to be a component of pleural fibrosis although there is no pleural effusion visible at this time. Diagnosis: chronic lower airway inflammation.

1 year old Quarter Horse gelding holding his head low.

There are moderate osteophytes at the facettes of C6-7 with an irregular, vertical radiolucent line superimposed over the joint. There is a step defect of the ventral vertebral canal at this level. A collimated projection was requested and showed the osteophytes to extend cranially over the lamina of C6. Differential diagnoses include a fracture and cervical spondylomyelopathy. Since there is no history of neurologic defecits a congenital vertebral malformation is less likely. Next steps could include nuclear scintigraphy to assess bone activity, CT to look at stenosis of the canal and search for fractures, or a myelogram to evaluate for spinal cord compression. A CT examination showed a fracture of the right vertebral facet of C6. The fracture line is irregular and widened, and there is varying bone density of the surrounding bone with periosteal proliferation. Diagnosis: chronic fracture with degenerative changes. The lucent area between the fragments and the osteolysis was likely due to a fibrous malunion. Comment: look for vertical lines since the normal facet joints are angled caudodorsally.

10 year old female neutered Basset Hound with lethargy and painful abdomen.

On radiographs, there is extensive bridging spondylosis of the lumbar spine. There is increased, streaky soft tissue opacity in the retroperitoneal space with a mass effect. There is also streaky soft tissue opacity in the peritoneal space, though the effect is much milder. On the v/d projection, the left kidney is enlarged. There is no normal left kidney visible. The descending colon is displaced ventrally supporting a left retroperitoneal mass. Radiographic diagnosis is retroperitoneal mass, with retroperitoneal and peritoneal effusion. Origins for the mass include the kidney, adrenal gland, or retroperitoneal tissues (hemangiosarcoma). Differentials include neoplasia (primary, metastatic) with effusion or hemorrhage, renal obstruction with uroretroperitoneum, pyelonephritis with associated inflammatory disease. Recommend abdominal ultrasound to positively identify the organ of origin and evaluate and sample tissue and fluid, and thoracic radiographs. Diagnosis: adrenal cortical carcinoma with hemorrhage.

This week’s collection of cases was a mixture – from GI to large animal radiographs to thorax. As usual, the residents did a great job of describing the findings, coming up with a radiologic diagnosis, and a list of differential diagnoses. These files are digital so make sure to look at the images as well.

Case 1

10 year old Bull mastiff with 3 weeks of intermittent vomiting. There is a severely dilated bowel loop in the dorsal right abdomen that contains striated foreign material. There is a tortuous, gas dilated loop cranial to this loop. The stomach apppears small. The peritoneal detail is poor. Differentials include chronic partial obstruction secondary to a stricture or mass, or a textile foreign body. Poor detail may indicate peritonitis from inflammation or bowel permeability. There is no free gas. Diagnosis: Schirrous adenocarcinoma with secondary chronic partial obstruction. Tip: Older dogs are less likely to ingest foreign bodies, so be on the lookout for causes of obstruction such as strictures or masses in the GI tract.

Case 2

Equine shoulder radiographs. 27 year old Arab gelding found non-weight bearing. The distal lateral radiograph of the shoulder did not include the glenohumeral joint. However, there is a possible bone fragment at the caudal aspect of the proximal humerus which is not visible on the more proximal views. Differentials include an artifact or a fracture fragment. Request additional radiographs more proximally with increased exposure. These, taken at a cranial 30 degrees medial to caudolateral oblique angle, demonstrated a fracture of the humeral tubercle with moderate caudal and distal displacement. Horses have a medial, central and lateral tubercle of the humerus. Diagnosis: Slab fracture of the humeral head parasagittal with medial tubercle fracture.

Case 3

5 year Arabian gelding. Large swelling with draining wound medial to left stifle. The radiographs are centered on the soft tissue swelling rather than the stifle. There is some motion artifact because the horse was painful. There is a metallic marker delineating the location of the wound. Differentials include hematoma or abscess. There is a linear lucent area in the soft tissues. Diagnosis: 6 inch wooden foreign body..

Case 4

1 year Yorkshire Terrier with polycythemia (77%). On thoracic radiographs, there is marked right sided cardiac enlargement. The aortic arch is enlarged on the d/v projection. One of the caudal lobar pulmonary arteries is blunted which may indicate pulmonary thromboembolism. The diagnosis is a congenital cardiac anomaly. Differentials include a right to left shunt including PDA, VSD, tetralogy of Fallot. Next steps could include non-selective angiography or echocardiography with bubble study, or nuclear scintigraphy. Using echocardiography, bubbles will bypass the lungs and appear in the abdominal aorta.

Case 5

2 month old St Bernard found wet and cold in the house (no images available). The patient presented dyspneic and was placed on the ventilator. Thoracic radiographs showed an alveolar pulmonary pattern in the caudodorsal lungs. A catheter is present in the cranial vena cava and there is an endotracheal tube in the trachea. There are also electrical leads on the chest wall. The most likely differential diagnosis is non-cardiogenic pulmonary edema secondary to asphyxiation, near drowning or electrical shock. Embolic pneumonia is less likely. Diagnosis: Non-cardiogenic pulmonary edema from falling in swimming pool.

This week at KCC we had some interesting and unusual cases. They were all on film, so I’m afraid there aren’t any radiographs to look at. Read the description and decide what you would do before reading the answer. In these types of cases, you aren’t expected to get “the answer” but to provide a logical analysis and appropriate differentials.

Mature domstic short hair cat with 3 week history of respiratory distress

Thoracic radiographs showed a flattened diaphragm and hyperlucent lungs. On the d/v projection, the ribs were nearly perpendicular to the spine and the diaphragm had scalloped edges. The esophagus was markedly dilated with air, as was the stomach and small intestine. These findings of hyperinflation and aerophagia suggested an upper airway obstruction so neck radiographs were requested. In the larynx, there was a soft tissue opacity mass that was responsible for the upper airway obstruction. Differential diagnoses included neoplasia (lymphoma, squamous cell carcinoma), granulomatous disease, and edema. Diagnosis: lymphoma.

9 month old domestic long hair cat with a heart murmur

The heart was markedly enlarged on both the lateral and d/v projections. The shape of the cardiac silhouette resembled a peanut with a waist between the enlarged atria and ventricles. The heart occupied more than 50% of the thorax on the d/v projection. The pulmonary arteries and veins were enlarged. On the edge of the radiograph, the fundus of the stomach was visible on the right side. Differential diagnoses included congenital heart disease such as vsd and abnormal valves, as well as PDA or VSD causing a left to right shunt. Secondary diagnosis: Situs inversus. Echocardiography revealed a single atrium and single ventricle with a VSD. Note: This type of case is not well diagnosed on radiographs beyond severe, congenital heart disease. Complex cardiac anomalies can be associated with situs inversus.

23 year old Morgan gelding with anorexia and weight loss

Thoracic ultrasound: There was marked echogenic pleural effusion with visible strands of the pericardial-diaphragmatic ligament. In the cranial thorax, there was a lobular mass with relatively uniform echogenicity. Differential diagnoses for the mass were neoplasia, most likely lymphoma, hemangiosarcoma, melanoma, or other neoplastic disease. Pleural fluid was non-diagnostic. A tissue sample was obtained by thoracoscopy. Diagnosis: anaplastic carcinoma.

This week’s KCC was about practicing interpreting an ultrasound video. It’s part of the oral exam, and it can be very disconcerting to watch someone else “drive”. There’s always something you want to see that they keep moving past! But it’s good practice to do the interpretations to orient yourself, describe what you see, and put it together with the history to make your interpretation.

Case 1

13 year old Siamese cat with lethargy. This scan started at the liver, which was enlarged and hypoechoic. The gall bladder was moderately distended, as was the common bile duct. The CBD was tortuous and looped back on itself before joining the duodenal papilla. There was no obvious mass at the papilla. The pancreas was mildly enlarged and hypoechoic but did not appear inflamed. The pancreatic duct was also enlarged. The diagnosis was chronic partial obstruction of the common bile duct, and differentials included inflammatory disease, neoplasia or calculus. The liver and pancreatic changes suggested chronic inflammation as is common in this group of diseases in cats. One year later, the changes looked similar, so inflammatory disease was the most likely diagnosis.

Case 2

11 year old Golden Retriever who had a red eye for two weeks and now has a painful eye. The ultrasound scanned through the globe. The anterior chamber and lens were identified. The vitreous body contained a hyperechoic, round mass that appeared to have strands connecting it to the iris and also touched the choroid at the back of the globe. The retina was not visible and the vitreous was clear. The most likely differential was neoplasia, since the vitreous was anechoic and showed no evidence of inflammation. Possible origins of the mass were the iris (melanoma) and the choroid. Diagnosis: melanoma originating from the iris.

Case 3

7 year old bull terrier with a mass on the neck. Orientation was difficult in this case. The scan appeared to be from lateral, with the mandibular salivary gland visible with a spleen-like echotexture in the cranial portion of the image. Caudal to the gland, there was a thin-walled, fluid-filled structure. The fluid was echogenic and the cystic area had complex septations. There were several small calculi in the far field that produced acoustic shadowing. There was a duct leading from the salivary gland into the cyst and it contained a calculus. Diagnosis: sialocele with sialoliths.

The majority of this week’s cases have a musculoskeletal theme. They were all on film radiographs so no images this time.

Case 1

2 yr male neutered Border Collie with lethargy and vomiting. On the abdominal images, there is increased soft tissue opacity in the retroperitoneal space with a mass effect displacing the colon ventrally. There are several segments of small intestine that are mildly gas dilated but not pathologic. Differentials for the retroperitoneal space include hemorrhage (coagulopathy, mass), urine, inflammatory (leptospirosis). Diagnosis: Rodenticide toxicity.

Case 2

2 week old colt lame in the right pelvic limb. There is an ill-defined lucency in the distal lateral femoral condyle on the craniocaudal projection. There is also soft tissue opacity within the joint indicating effusion. Request radiographs of the opposite stifle to compare for a bilateral lesion (developmental) or unilateral (infectious). The left stifle is normal. Differentials for this lesion include osteomyelitis and septic arthritis, less likely a developmental lesion such as OCD considering the location in the lateral condyle. Comment – ultrasound of the stifle to evaluate the meniscus would be appropriate for prognostic information.

Case 3

2 year old TB filly. Acute right hind limb lameness for 11 days. Worsened to 5/5 lame in last few days. Ultrasound of right hind limb just proximal to the fetlock. There is peritendinous lacy tissue between the SDFT and skin, and between the two tendons, likely within the digital sheath. There is an expansile area in the straight sesamoidean ligament which can be explained by non-weight bearing and reduced tension. Differentials are SDFT desmitis at the level of the fetlock with tenosynovitis and SSL desmitis. Diagnosis: septic tenosynovitis with communicating external wound. Comment: the proliferative synovium has a typical lacy appearance and does not swirl as an effusion would.

Case 4

Adult female neutered DSH with 1 week history of pelvic limb lameness and lethargy. Distal soft tiissue swelling around digits 3 and 4 with lysis of P3. Differentials include metastatic pulmonary carcinoma, cellullitis and osteomyelitis, soft tissue neoplasia with local invasion, trauma. Diagnosis: metastasis from primary pulmonary adenocarcinoma. Comment: This is a classic! Pulmonary adenocarcinomas have a predisposition to metastasize to digits in the feline.

Case 5

6 month old male Labrador Retriever with progressive swelling of the right mandible. Skull radiographs – there is a productive lesion originating from the caudal 2/3 of the right mandible. The periosteal reaction is several cm thick, dense, and irregular. Differentials include craniomandibular osteopathy although it is not a typical breed or distribution. Given the assymetry of the lesion, differentials should include infectious causes such as osteomyelitis, osteoblastic osteosarcoma. Diagnosis: CMO. It did not recur after surgery 6 months later.

Known Case Conference

This week at KCC we moved back to the digital realm so I have some images for you to look at. Though I do need to save some to surprise our residents with next year!

Case 1

This case is a 10 year old female neutered Jack Russell Terrier with a 6 month history of coughing. These radiographs are really impressive! On thoracic radiographs, there are multiple, large, mineralized pulmonary masses in all lung lobes. There are also some smaller nodules in the right caudal lung lobe. Differential diagnoses included metastatic osteosarcoma, primary lung tumor with multiple metastases, granulomas (fungal, parasitic), and other metastatic disease. Diagnosis: Primary pulmonary carcinoma.

Case 2

Next was a 9 year old female neutered Bernese Mountain Dog with coughing and decreased appetite. There are multiple soft tissue masses in the pulmonary parenchyma, including the caudal subsegment of the left cranial lung lobe, right cranial lung lobe, and right middle lung lobe. The cranial mediastinum is widened and increased in opacity, indicating lymphadenopathy. The increased soft tissue opacity and widening of the main stem bronchi indicate hilar lymphadenopathy. Differential diagnoses included histiocytic sarcoma and granulomatous disease. This was a very typical appearance of histiocytic sarcoma, with ill-defined and well-defined pulmonary masses, lobar infiltration, and lymphadenopathy. Faculty commented that Roentgen findings of masses, lymphadenopathy and alveolar pattern should lead you to differentials of PIE and histiocytic sarcoma.

Case 3

This case of a 2 year old Labrador Retriever was an old one, still on film radiographs. The dog presented with ascites. The thoracic radiographs were relatively normal, with the exception of an enlarged caudal vena cava. The abdomen included was distended and had poor detail, consistent with the history of ascites. Differentials included common congenital heart diseases such as septal defects and left to right shunts causing right heart failure. But if you think about it, all of those diseases result in an enlarged heart which this was not. Our second year resident nailed it by diagnosing cor triatriatum dexter. In this congenital condition, there are septae within the right atrium that block inflow of blood from the caudal vena cava and cause obstructive disease. Rare, but classic!

We had another great collection of cases at this week’s KCC. Here are some of the highlights.

Case 1

3 year old female spayed cat with sudden onset of left hind lameness. On pelvic radiographs, there were no abnormalities seen. A “frogleg” view was requested to better evaluate the coxofemoral joints. There was discontinuity of the femoral neck, indicating a fracture. The femoral neck was otherwise normal. Diagnosis: fractured left femoral neck. These fractures can be difficult to see, as well as those involving the physis between the femoral head and neck. The v/d flexed hip projection, or frogleg projection, can give you another perspective with which to detect the fracture.

Case 2

5 year old female neutered Rottweiler with weight loss and inappetance. On thoracic radiographs, there was increased soft tissue opacity in the right cranial thorax, as well as in the accessory lung lobe. The ribs in the right cranial thorax were expanded compared to the other side. The soft tissue opacity contacted the right thoracic wall with a broad base, but a true pleural sign was not evident. There was no pleural effusion visible. Differential diagnoses included neoplasia (histiocytic sarcoma), eosinophilic granulomatosis, and abscesses or granulomas. The pleural or pulmonary origin of the right cranial mass was difficult to determine. Diagnosis: Histiocytic sarcoma. Faculty comments included that pleural masses are often accompanied by effusions. V/d oblique projections can also be obtained to try to demonstrate a pleural sign.

Case 3

2 year old male neutered domestic short haired cat with 2 week history of lethargy and anorexia. On thoracic radiographs, there was a large mediastinal mass in the dorsal portions of the cranial and caudal mediastinum. The soft tissue opacity mass was displacing the trachea ventrally. An esophagram showed no deviation or obstruction of the esophagus. Differential diagnoses included infectious/inflammatory (abscess, granuloma) and neoplastic (lymphoma) causes. Diagnosis: cryptococcosis. Radiologists commented that large mediastinal masses are often cryptococcus or lymphoma. The dorsal distribution was quite different from more commonly seen thymoma and lymphoma cases.

After a few weeks’ break from KCC while the senior residents were off studying for boards, we are back with more great cases. This group of cases had a urinary tract theme.

Case 1

A mature cat with azotemia underwent an excretory urogram at the referring veterinarian. During the procedure, the cat started vomiting. There were two radiographs of the abdomen. The right kidney was enlarged and opacified with contrast medium. The left kidney was faintly visible and very small. The urine was also contrast enhanced. The ureters appeared normal. The liver was enlarged and had increased opacity relative to the other abdominal organs. Differential diagnoses included compensatory hypertrophy of the right kidney due to atrophy of the left, and contrast induced renal failure, ureteral obstruction, or hypotension. CIRF was considered to be most likely because of the onset of vomiting during the procedure. Hypotension may have been a predisposing or concurrent factor.

Why was the liver enhanced? Biliary excretion of contrast is the alternate route to urinary excretion. The persistent renal enhancement after several hours indicated renal failure, so the liver took over extracting the iodine from the blood.

Case 2

13 year old female Pekinese straining to urinate. On survey radiographs, there was a soft tissue mass in the caudal abdomen displacing the colon dorsally. This may have been the urinary bladder, or part of the reproductive tract. A vaginourethrogram was performed, and showed a dilated, contrast filled vagina with a large intramural filling defect dorsally, and a small bladder ventrally. The mass was located in the pelvic inlet and partially in the caudal abdomen. Differential diagnoses included a neoplasia or hematoma affecting the vaginal wall. Diagnosis: Leiomyoma of the vagina. This case was difficult to interpret because the dilated vagina resembled the shape of the bladder. However, it was located dorsally to the second structure (the bladder) and both the vagina and the ureter could be followed to the vestibule without crossing over each other.

Case 3

3 year old female spayed Rottweiler dribbling urine. Survey radiographs showed no abnormalities. An excretory urogram was requested to rule out an ectopic ureter as the cause for incontinence. The study showed normal kidneys and ureters. The bladder was gourd shaped, with a symmetric narrowing as it passed into the pelvis. The trigone was located in the mid portion of the pelvic canal. Both ureters entered the trigone normally. Diagnosis: pelvic bladder. These are typically slightly misshapen due to their location, and are caudally positioned.

This week at KCC we had some excellent equine cases that generated plenty of discussion.

Case 1

8 year old warmblood that became lame in the right hind leg at a show. On radiographs of the fetlock, there was an ill-defined lucency of the border of the medial metatarsal condyle seen best on an oblique projection. Additional views were requested to better evaluate the condyles, including a flexed lateral and the 125-degree dorsopalmar metacarpal skyline projection (125″ DPMS) (see reference). The lesion was not seen on either of these views. The next suggestion was cross sectional imaging. On CT, there was marked sclerosis of the dorsal distal medial metacarpal condyle and an impressive defect in the subchondral bone.

Discussion points included the anatomy of the fetlock joint. There are really two articulations, MTIII cranially articulates with P1 and MTIII caudally articulates with the sesamoid bones. The 125-degree dorsopalmar metacarpal skyline projection (125″ DPMS) was designed to highlight the caudal aspect of the joint, or the articulation with the sesamoids. The fact that the lesion was not seen on this view meant that it had to be involving the cranial portion of MTIII. This was confirmed with the CT scan.

Additional comments were that you could see this area of the fetlock with ultrasound, holding the limb in a flexed position. The lesions would be visible and the images would provide very valuable information.

The special projection article is worth a look, there are great diagrams of the angled projections of the fetlock. ACVR members have access through the ACVR website.

Hornof WJ, O’Brien TR. Radiographic evaluation of the palmar aspect of the equine metacarpal condyles: a new projection. Journal – American Veterinary Radiology Society 1980;21:161-167.

Case 2

5 year old Quarter Horse mare with mandibular swelling. Two oblique lateral projections of the skull showed a marked thickening of the mandible ventral to the right third premolar. The roots of the premolar were blunted and irregular, with areas of increased and decreased lucency superimposed. The periodontal ligament was absent ventral to the roots but was of normal width adjacent to the tooth. Differential diagnoses included a tooth root abscess, possibly caused by trauma or a developmental anomaly since the horse was so young. It also may have been abnormal tooth root development post-trauma. The opposite maxillary tooth was overgrown. A CT showed the marked mandibular thickening, and a hook-shaped tooth root oriented medially at a 90 degree angle. The tooth was extracted and was not infected. Comments included that the normal width of the periodontal ligament indicated infection was unlikely; it tends to widen with inflammation.

Case 3

The first image in this case was nuclear scintigraphy of the carpus. There was marked increase in uptake in the proximal metacarpus that extended from the dorsal to palmar surface on the lateral projection. There was also mild uptake in the proximal left metacarpus. Differentials included suspensory ligament desmitis or avulsion, and radiographs were requested. There were two faintly visible vertical, radiolucent lines in the proximal right metacarpus along with sclerosis. A collimated view was requested but it did not enhance visibility of the lesions. Diagnosis – proximal metacarpal fracture.

During the discussion, several good points came out. First, a pure suspensory desmitis should not cause increased uptake in the entire proximal metacarpus. It should be limited to the caudal aspect. Second, additional oblique DP radiographs with very small angle increments can often reveal the fractures when the x-ray beam lines up with them. No cross-sectional imaging was recommended for this horse because of the risk of catastrophic fracture during anesthesia.

There were some really challenging cases at KCC this week. Here are a few summaries;

Case 1

11 year old Golden Retriever, lame on the right hind limb. Here’s a link to the case; imagine you are in the hot seat and give an oral description, list of differentials, and next steps.

Case 2

8 year old Boxer with mass on the right thorax. On thoracic raidographs, there was increased soft tissue opacity in the cranial mediastinum causing the cardiac silhouette to be displaced caudally. The carina was between the 7th and 8th ribs. There was also pleural effusion in the right hemithorax, and a lytic rib with associated body wall and pleural mass. Several sternebrae were lytic and collapsed. Differential diagnoses for mediastinal mass and multiple aggressive bone lesions included primary bone neoplasia with metastasis, hemangiosarcoma, round cell tumor and chemodectoma. Diagnosis: Lymphoma.

Case 3

3 year old female neutered cat with tachypnea. There was pleural effusion in the left hemithorax with retraction of the lung lobes and pleural thickening. The left caudal lung lobe had increased opacity and an irregular gas opacity visible on both projections. Differentials were pyothorax and lung abscess with secondary pyothorax. Further diagnostics could have included ultrasound or a horizontal beam radiograph to look for a fluid-gas interface. Diagnosis: pulmonary abscess with secondary pyothorax.

This week was all equine with some great cases to challenge the residents.

Case 1

15 year old Thoroughbred gelding lame in the right hind limb. Lameness resolves with an abaxial sesamoidean local anesthetic block. There was a crescent shaped, smoothly marginated defect in the dorsolateral margin of P3. There was a subtle defect in the sole of the hoof at this location. Differential diagnoses: keratoma, with possible abscessation. This horse had a keratoma and an associated abscess. There is debate as to whether the keratoma is the cause or result of inflammation in the foot.

Case 2

9 year old Thoroughbred jumper with chronic grade 2/5 lameness of the right front limb. Positive to fetlock flexion, partial block of the lameness with a PD. On radiographs of the fetlock and foot, there were osteophytes on dorsal P2 and the extensor process of P3. There was also an irregular lucent area parallel to the joint surface of lateral P3. There was sclerosis surrounding this area on the DP and the lateral projections. There appeared to be a lucency that provided communication between the cystic area and the coffin joint. Diagnosis: osseous cyst-like lesion of P3 with communication to the coffin joint. This was most likely a congenital lesion, though trauma could not be ruled out. Further diagnostics could include an arthrogram to prove joint communication.

Case 3

2 year old Thoroughbred colt in race training. 1/5 lame left front, positive to fetlock flexion. On fetlock radiographs, there was a subtle radiolucency of MC3 visible on the dorsolateral-palmaromedial oblique projection, and very faintly seen on the lateral projection. A flexed lateral projection was requested, which clearly showed a radiolucent lesion of the sagittal ridge of MC3. Diagnosis: Osteochondrosis.

This week’s KCC was hosted by our large animal ultrasonographers, Mary Beth Whitcomb and Betsy Vaughan, and they brought some great cases to challenge the residents with.

Case 1

18 month old Standardbred colt who had both front legs caught in the stall yesterday. Lame on the left front limb. The ultrasound images included lateral and medial aspects of the fetlock. On the medial side, there was enlargement and disruption of the collateral ligament near its insertion. The ligament had mottled hyperechoic and hypoechoic areas in this region. Diagnosis: medial collateral ligament desmitis. Recommendations included stress radiographs of the fetlock to evaluate for instability. There is a long and a short component to the collateral ligament, and the long component was featured in these images. The short component runs slightly transverse so may not be seen in the same image.

Case 2

21 year old retired Thoroughbred gelding, grade 4/5 lame on the left hind limb for 2 days. Images of the left hind pastern were presented. The superficial digital flexor tendon was enlarged on the plantaromedial side with a hypoechoic core lesion that occupied 50% of the tendon cross section. This was clearly visible on the sagittal images as well. The lesion involved the medial branch of the SDF at its insertion. Diagnosis: Moderate insertional tendinitis of the medial branch of the SDF. When looking at the lateral branch, there were also mottled areas at the insertion as the tendon fibers splayed outwards as they attached. These are normal findings in this area.

Case 3

11 year old Thoroughbred gelding with grade 3/5 lameness of the right hind limb, of unknown duration. Local anesthesia: abaxial block 0% improvement, distal intertarsal/tarsometatarsal 0% improvement, proximal metatarsal 75% improvement. Ultrasound images of the plantaromedial aspect of the metatarsus extended from 18-28 cm distal to the point of the hock. There was a hypoechoic lesion involving 50% of the cross sectional area of the suspensory ligament. Some normal hyperechoic fibers remained in the central portion of the ligament. Diagnosis: suspensory ligament desmitis. Interesting anatomy points were that the SDF travels over the point of the hock while the DDF travels over the sustentaculum tali medially. So in the proximal images, only the DDF was visible. As the images moved distally the SDF came into view. Recommendations included radiographs to look for sclerosis or avulsion fractures at the origin of the suspensory ligament.

This week we had some good old fashioned films to look at. No powerpoint, and everyone clustered around the viewboxes to get a look at them. We also gave the residents two at a time with a 15 minute time limit. It’s good practice for letting the last case go and moving on to the next one.

Case 1

Case 1 was a 2 year old female spayed cat with coughing. The heart was enlarged, as were the pulmonary arteries. There was also a diffuse bronchial pattern. The most likely diagnosis by far was heartworm. Recommendations included echocardiography to look for adult worms. Diagnosis: heartworm disease.

Case 2

Case 2 was a 9 year old male neutered DSH with dyspnea. There was a broad-based, soft tissue opacity in the cranial thoracic tracheal lumen. The remainder of the thorax was normal. Differentials included lymphoma, carcinoma, granuloma and stricture. Endoscopy or cervical ultrasound were options for further workup. Diagnosis: adenocarcinoma.

Feline tracheal tumors are uncommon, but most are lymphoma and carcinoma.
Carlisle CH, Biery DN, Thrall DE. Tracheal and laryngeal tumors in the dog and cat: literature review and 13 additional patients. Veterinary Radiology 1991;32:229-235.

Case 3

Case 3 was a 5 year old male neutered Jack Russell Terrier with difficulty swallowing. On thoracic radiographs, there was a soft tissue opacity in the caudal mediastinum that looked laminar with some gas between the layers. It was depressing the caudal mainstem bronchi. An esophagram was requested and contrast flowed around the cranial portion of the mass. Differentials included esophageal neoplasia, diverticulum, less likely foreign body. Diagnosis: Esophageal diverticulum secondary to an esophageal foreign body obstruction the year previously.