DLCO correlates with intestinal inflammation in ulcerative colitis, but albuminuria does not

The aim of this study was to evaluate the frequency of carbon monoxide diffusing capacity (DLCO) impairment and microalbuminuria in patients with active ulcerative colitis (UC) and to assess whether these nonexpensive and noninvasive tests correlate with intestinal inflammation.

A prospective observational study was set up at the Fiorenzuola Hospital and performed during a 4-year period. We enrolled 30 consecutive subjects with clinical and histological diagnosis of active UC and 20 healthy subjects matched for age and sex. After full colonscopic assessment with multiple mucosal biopsies, the clinical disease activity of each patient was quantified. A global spirometry and 24-h urine collection at rest to measure microalbuminuria were performed. Each biopsy specimen was assessed blindly by a histopathologist, who assigned a score according to the severity of enterocyte damage, cryptitis and acute and chronic inflammation of the lamina propria.

A latent pulmonary involvement with a reduction in DLCO was present in 20 patients (67%). A subclinical renal involvement with microalbuminuria was detected in 19 subjects (63%). The mean DLCO was 78.2+/-15.2 in Group 1 vs 94.7+/-13.1 in Group 2 (P<0.001). Microalbuminuria was 103.6+/-90.8 in Group 1 vs 57+/-31.7 in the control group (P=0.062). DLCO reduction correlated significantly with intestinal histopathological grading in Group 1 (r = -0.742, P< 0.001), although there was no correlation between microalbuminuria and histological grading (r = -0.273, P= 0.143).

Our data confirm that latent pulmonary involvement (DLCO impairment) and microalbuminuria are frequent in UC. The DLCO may provide a useful noninvasive indicator of colonic inflammation in subjects with UC and concomitant subclinical lung involvement.