Background: Conflicting data exist about proteinuria in inflammatory bowel
diseases. It is still unclear whether the occurrence of proteinuria in infl
ammatory bowel disease patients is an extra-intestinal manifestation of dis
ease or the result of adverse effects to medication, especially to aminosal
Methods: A total of 95 patients (51 with Crohn's disease and 44 with ulcera
tive colitis) were enrolled in the study. Disease activity was assessed by
Crohn's Disease Activity Index (CDAI) or the Truelove index, respectively.
Urine was collected over 24 h and protein excretion of specific marker prot
eins for tubular (alpha1-microglobulin-alpha1-MG) and glomerular (albumin-A
lb, Immunoglobulin G-IgG) dysfunction was measured using a highly sensitive
Results: Out of 51 Crohn's disease patients, 20 showed elevated urinary alp
ha1-MG. The amount of alpha1-MGuria was strongly correlated to the CDAI (r
= 0.6, P < 0.001). Only four Crohn's disease patients showed slightly eleva
ted values for glomerular proteins in urine. Similar results were obtained
for ulcerative colitis: whereas only two ulcerative colitis patients showed
albuminuria, tubular proteinuria was detected in 28 out of 44 ulcerative c
olitis patients. Proteinuria was strongly dependent on disease activity (P
< 0.01) but was not related to ASA treatment.
Conclusions: Proteinuria of tubular marker proteins occurs in the majority
of inflammatory bowel disease patients and is related to disease activity r
ather than to ASA treatment. Tubular proteinuria seems to reflect a renal e
xtra-intestinal manifestation of inflammatory bowel disease and may serve a
s a new relevant marker of disease activity.