The objective of this study is to determine the prevalence of secondary lactose intolerance in renal transplant recipients (RTR) with chronic norovirus infection. In the investigators cohort of 1000 renal transplant recipients (RTRs) in the University Hospital of Zurich, the investigators are currently aware of 10 patients with chronic norovirus infection, which was proven by positive polymerase chain reaction (PCR) analysis of recent stool samples, whereas chronic virus shedding is defined as more than two PCR positive samples in an interval of at least one month. Concomitant viral (other than norovirus), bacterial or parasitic (particularly Gardia lamblia) intestinal infections are excluded by negative stool cultures and PCR analyses, respectively. Main exclusion criterion for the present case series is a concomitant intestinal infection (other than norovirus) and primary lactose intolerance, which is previously excluded by absence of the CC genotype of the DNA variant -13910 T/C upstream in the LCT gene. After obtaining written and oral informed consent, the investigators perform a lactose hydrogen breath (LH2BT) test and a lactose tolerance test (LTT) in all eligible RTRs with proven chronic norovirus infection irrespective of current abdominal symptoms. The study population (N=10) is divided into two groups according to the gastrointestinal symptoms (asymptomatic versus symptomatic, such as chronic diarrhoea or diffuse abdominal discomfort). The investigators chose the cut-off three or more stools per day as indicative of diarrhoea for the purpose of this study. RTRs with otherwise unexplainable chronic diarrhoea but absent norovirus infection serve as control group (N=10).
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Lactose intolerance
Timeframe: 4 weeks