Follow-up after urinary diversion.

With modern forms of urinary diversion being widely employed during recent years, the awareness of possible complications and appropriate follow-up strategies gains rising importance and current follow-up strategies are reviewed herewith. Follow-up investigations after urinary diversion have to address possible surgical complications, metabolic changes as well as the risk of secondary malignancies in the incorporated bowel segments. The most important and possible deleterious surgical complication is upper tract dilation and obstruction following ureteroenteric anastomotic stenosis and occurs in 2-30% depending on the surgical technique and evaluated series. The most appropriate follow-up study to detect upper tract dilation is ultrasonography while the associated obstructional component can best be estimated by functional renographic studies (MAG(3) renal scan). The significance of reflux associated with urinary diversion remains controversial although experimental studies and clinical observations suggest a risk of renal functional deterioration associated with reflux which is certainly true in ureterosigmoidostomy following pyelonephritic changes. Possible metabolic changes include hyperchloremic metabolic acidosis and problems related to malabsorption due to bowel resection and incorporation of bowel segments into the urinary tract. The incidence of hyperchloremic acidosis is related to the form of urinary diversion, being higher in continent forms than in incontinent diversions, while hyperchloremic metabolic acidosis is most frequently encountered in ureterosigmoidostomy. While acute complications of metabolic acidosis may encompass hyperventilation as well as severe changes of serum electrolytes and acid base balance leading to cardiac arrhythmias necessitating immediate hospital treatment with intravenous alkalinizing, chronic acidosis may lead to osteopenia through hypocalcemia and stimulation of osteoclastic activity. Metabolic acidosis can be best detected by regular blood gas analysis. To prevent these complications prophylactic administration of alkalinizing agents (e.g. potassium citrate) should be readily performed. Malabsorption of bile acid strongly correlates with the length of ileum resected and can induce both chologenic diarrhea and malabsorption of liposoluble vitamins (A, D, E, K). Vitamin B(12) is exclusively absorbed in the distal ileum, serum levels therefore may be reduced following resection of distal ileum. This will not occur during the first 3-5 years following diversion because B(12) deposits usually will last for this period. Later, however, serum levels of vitamin B(12) should be checked annually while others favor routine substitution of this vitamin. The incidence of cancer occurring at the ureterointestinal anastomosis seems to be highest in patients with ureterosigmoidostomy varying between 2 and 29% with polypoid benign lesions being more frequent. The most common type of tumor is adenocarcinoma which has also been reported in colonic and ileal conduits as well as augmentation cystoplasty using either colon or ileum. Since the time interval between surgery and cancer occurrence is longer than 10 years, the newer forms of continent diversion theoretically also inherit the risk of tumor formation, which, however, has yet to be established because these diversions are only in wide use since 10 years. Currently, annual endoscopic controls are recommended in those patients with diversions where feces and urine are in contact with urothelium starting 5 years after surgery. Although formal guidelines for follow-up after urinary diversion have not yet been established by the working group on oncology of the German urological association, this paper suggests a follow-up strategy addressing surgical complications, metabolic changes and the risk of secondary malignancies.