Fecal radioiodide excretion following intravenous injection of 131-I-albumin and 125-I-immunoglobulin G in chronic inflammatory bowel disease. An aid to topographic diagnosis.

Simultaneous studies with 131-I-albumin and 125-I-immunoglobulin G (IgG) were made in 48 cases of chronic inflammatory bowel disease. Twenty-one had ulcerative colitis and 27 had Crohn's disease which was confirmed at laparotomy in every case. Intestinal protein loss was measured simultaneously by means of 59-Fe-iron dextran in 44 patients. All patients had abnormal intestinal protein loss. A high correlation was shown between fecal 59-Fe clearance and fractional catabolic rate of albumin, confirming the validity of 59-Fe-iron dextran as a test substance to measure intestinal protein loss. Fecal radioiodide excretion of 131-I from 131-I-albumin (A) and 125-I from 125-I-IgG (G) was significantly different in ulcerative colitis and Crohn's disease. The ratio G/A was close to unity (smaller than 1.60) in ulcerative colitis and Crohn's disease with exclusive or predominant involvement of the colon, whereas it was high in Crohn's disease of the small intestine and highest in cases with jejunal involvement. Thus, the ratio may be valuable in topographic diagnosis of chronic inflammatory bowel disease. A high ratio was found in 2 patients with Crohn's disease of the small intestine and normal radiography of the small intestine, and a low ratio was present in 7 cases of ulcerative colitis with normal radiographic findings. In all 9 patients with normal radiography, fecal 59-Fe clearance was elevated as evidence of abnormal intestinal protein loss. No correlation was present between the size of protein loss and the pathoanatomic extent of the lesions on subsequent laparotomy in 25 patients with Crohn's disease. Fecal radioiodide excretion (131-I from 131-I-albumin and 125-I from 125-I-IgG) was positively correlated with diarrhea (daily stool mass) in both ulcerative colitis and Crohn's disease. Intestinal protein loss was not.