Lymphoid depletion in ileal loops: mechanism and clinical implications.

Recent long-term follow-up studies of children undergoing ileal loop urinary diversion have shown a number of complications arising in these patients: recurrent urinary tract infections, deteriorating renal function, and late midloop stricture. We suggest that all three may be related to the same underlying problem, namely, a severe depletion of lymphoid elements in the intestine. In both clinical and animal studies urine exposure to intestinal segments resulted in a marked depletion of lymphoid elements from the Peyer's patches and from beneath the intestinal villi in the intestine. In addition there was an associated hypertrophy of the lymph nodes in the ileal loop mesentery. When the intestine was no longer exposed to urine, there was a prompt regeneration and reappearance of the lymphoid elements. The lymphocytes seemed to "home in" on the submucosal areas and reform Peyer's patches once the urine was removed. The hyperplastic lymph nodes in the ileal loop mesentery regressed when urine exposure was removed. Conventional treatment of ileal loop infections focuses on the upper urinary tracts. Mid-loop stenoses are treated by resection and creation of a new ileal loop conduit. Local therapy in the form of antibiotics and/or steroid enemas may relieve some late midloop obstruction and prevent further damage to renal parenchyma.