2005 Radiology Exam - Alternate Imaging Case 1

Information Provided to Candidate
1. Feline: DSH, 11 year old female spayed
2. 3 month history of a persistent urinary tract infection
3. Survey radiographs and an excretory urogram were done.
4. 1cc/lb of Conray 400mgI/ml was administered for the excretory urogram.
5. Survey radiographs and images at 0, 5, 20, 40 and 60 minutes were provided.

State the radiographic findings.

• Give a concise assessment.
• Any further imaging studies needed? If not, why not? If yes, what studies are indicated and why?

See images below. Click to enlarge.

Findings Expected from Candidate
On survey radiographs, not shown here, a small right kidney with a focus of mineralization overlying the right kidney were readily apparent. On the excretory urogram, there is prolonged persistence of the nephrogram phase and a markedly delayed and poor pyelogram phase in both kidneys. The small right kidney is abbreviated and distorted at the cranial pole. There is a progressive increase in opacity over time of the small bowel lumen.

Conclusion Expected from the Candidate

• The prolonged nephrogram phase and delayed and poor pyelogram phase are consistent with renal dysfunction and in this scenario, contrast medium induced renal failure should be the primary differential. This is further supported by the presumed gastrointestinal excretion of contrast medium (so called alternate route of excretion). The small irregular right kidney is likely secondary to a cranial pole infarct.
• A cause for the persistent urinary tract infection is not apparent on this study. The probable contrast medium induced renal failure should be addressed immediately with appropriate medical management. Additional radiographs after initiation of therapy may allow some assessment of therapy and may better show the collecting system and ureters. A 60 minute study (after initiation of aggressive fluid therapy) was available on request.
• A double contrast cystogram or sonogram may be indicated to better assess the bladder as a cause for the urinary tract infection, once the patient is stabilized.

Summary of Overall Candidate Performance

• Many candidates did not see either the persistent nephrogram or the delayed/poor pyelogram. Some who saw the poor pyelogram phase did not provide a reasonable explanation for this finding. The differential lists provided for the morphology changes in the right kidney were extensive. Many candidates focused on this radiographic finding and failed to mention the left kidney.
• Remember, when evaluating an excretory urogram, changing renal opacity is just as important as morphology and, in this case was the critical radiographic finding. Many candidates failed to relate the radiographic findings back to the history in planning the next step.