Intestinal permeability tests and integrity of the small intestinal mucosa

Tropical sprue in 2014: the new face of an old disease

Tropical sprue (TS), once known to be a common cause of malabsorption syndrome (MAS) in India and other tropical countries, is believed to be uncommon currently in spite of contrary evidence. Several recent studies from India showed TS to be the commonest cause of sporadic MAS in Indian adults. TS is diagnosed in patients presenting with suggestive clinical presentation, which cannot be explained by another cause of MAS and investigations revealing malabsorption of two unrelated substances, abnormal small-intestinal mucosal histology, which responds to treatment with antibiotics such as tetracycline and folic acid. There is substantial overlap between TS and postinfectious irritable bowel syndrome. There have been several advances in epidemiology, pathogenesis, and diagnosis of TS, hitherto an enigmatic condition.

Abnormal small intestinal permeability in patients with idiopathic malabsorption in tropics (tropical sprue) does not change even after successful treatment

BACKGROUND

Though tropical sprue (TS) is common in tropics, studies on small intestinal permeability (SIP) in TS are scant.

METHOD

SIP was evaluated using (1)H nuclear magnetic resonance (NMR) spectroscopy of urinary lactulose and mannitol in 24 patients with TS (22 before and 15 after treatment with tetracycline and folate) and in 31 healthy subjects (HS). Effect of treatment of TS on SIP and its relationship with outcome were studied.

RESULT

Subjects were comparable in terms of age and gender. Before treatment, urinary lactulose (0.24 mmol, 0-1.09 mmol versus 0.09 mmol, 0-0.68 mmol, P=0.02) and lactulose-to-mannitol (L/M) ratio (0.11, 0-0.41 versus 0.042, 0-0.26, P=0.001) were higher in TS than in HS, though mannitol was comparable (2.7 mmol, 0.61-10.5 mmol versus 3.8 mmol, 1.3-16.4 mmol, P=0.08). Patients improved after treatment [stool frequency (9, 4-20/day versus 1, 1-2/day, P<0.0001), weight (44.4, 32-69 kg, versus 56, 39-84 kg, P<0.0001), fecal fat (10.1, 6-26 g/24 h versus 4.4, 3.0-6.7 g/24 h, P<0.0001), D-xylose (0.57, 0.28-1.2 g/5 g/5 h versus 1.1, 0.2-2.1 g/5 g/5 h, P<0.0001), and small intestinal bacterial overgrowth (SIBO) resolved in 10/24 (41.7%) versus 1/15 (6.6%), P=0.02]. Though urinary lactulose (0.17, 0-4.3 mmol versus 0.09, 0-0.68 mmol, P=0.11) and mannitol (2.17, 0.8-36.7 mmol versus 3.84, 1.3-16.4 mmol, P=0.06) were comparable, L/M ratio was higher in TS than in HS (0.09, 0-0.22 versus 0.042, 0-0.26, P=0.002). L/M ratio was more often abnormal (cutoff 0.078) in TS than in HS [14/22 (63.6%) versus 3/31 (9.7%); P=0.0001], which persisted even after treatment [9/15 (60%) as compared with HS; P=0.0006]. Persistently abnormal SIP was associated with less weight gain and frequent stools following treatment.

CONCLUSION

SIP is often abnormal in TS and remains unchanged even after successful treatment that was associated with less weight gain and more frequent stool.