DMSA Case 4 Answers

1)Describe the appearances.

There is decreased uptake in the right kidney, which appears smaller than the left. There is considerable activity remaining within the blood stream, evidenced by prominent heart, lung and liver activity. Of note is marked activity within the left colon, sigmoid and rectum. There is also a square photopaenic area in the low mid-line.

2)Can you explain them?

The patient has had a cystectomy and ureterosigmoidostomy - the activity in the large bowel is due to tracer in the urine. The systemic blood pool activity represents lack of renal uptake, most likely to a combination of poor renal function and metabolic acidosis (see below). The patient was wearing a metal belt-buckle.

3) What is this patient more at risk of?

From 1920 to 1965, ureterosigmoidostomy was the operation of choice for patients with either bladder exstrophy or for urinary diversion following cystectomy. This procedure had the advantage that the anal sphincter could maintain continence of urine, while the rectum and sigmoid colon developed the ability to distend and contain a large volume of urine

It has been abandoned, as there are three major post-operative problems

Neoplasia. Following ureterosigmoidostomy there is a 500X increased risk of adenocarcinoma arising at the site of ureterocolonic anastomosis. This represents a 5% lifetime risk. The latent time of these lesions is usually 15-30 years but varies from 6 to 50 years postoperatively. Development time is significantly less in patients more than 40 years old. Even following urinary rediversion, there is still a risk of neoplasia at this site and lifelong endoscopic follow-up of the anastomotic site is necessary. For some reason, ileal conduits do not suffer from neoplastic complications
Metabolic disturbance. Patients suffer a variable amount of hypokalaemia and hyperchloraemic metabolic acidosis. This may be marked and life threatening or totally asymptomatic Infection.
Reflux of urine ± faeces may create problematic, recurrent pyelonephritis.

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