Keywords
multiplex PCR - post-transplant diarrhea - sapovirus
Introduction
Diarrhea is common in post-solid transplant individuals and adds to the morbidity
and mortality in such individuals.[1] While most diarrheal episodes occur early in the posttransplant period as acute
self-limiting gastroenteritis, rarely it can be recurrent or chronic in presentation.
The etiologies of diarrhea in post-solid transplant individuals can be broadly classified
into infectious and noninfectious causes.[1] Among the infectious causes a plethora of organisms including bacteria, viruses,
and protozoan parasites have been implicated. While drug-induced and posttransplant
lymphoproliferative disorder are notable etiologies in the noninfectious group. Guidelines
suggest an initial empirical treatment of diarrhea with appropriate fluid and electrolyte
management and an algorithmic evaluation if recurrent or chronic diarrhea occurs.[1]
Sapovirus, a single-stranded ribonucleic acid, nonenveloped virus belonging to the
genus Sapovirus within the Caliciviridae family, is commonly and increasingly being implicated in self-limiting acute diarrhea
in the community setting.[2] This increased recognition is due to improvement in molecular diagnostics, which
have enabled its differentiation from norovirus, another common virus implicated in
acute gastroenteritis belonging to the Caliciviridae family.[3] It is now also increasingly being recognized as emerging pathogen causing persistent
diarrhea in immunocompromised individuals, particularly in the post-renal transplant
setting.[4]
[5] In this report, we present two cases who presented with chronic diarrhea in the
post-renal transplant setting and were diagnosed as having sapovirus-associated diarrhea.
Case 1
A 74-year-old lady with deceased donor renal transplant 12 years back presented with
chronic diarrhea for 9 months and significant weight loss of 10 kg in the outpatient
clinic in March 2025 ([Table 1]). She denied any fever, vomiting, or blood in stools. She was on prednisolone 5 mg,
mycophenolate mofetil (MMF) 500 mg twice a day, and tacrolimus 1.5 mg a day. Her diarrhea
was evaluated with stool routine microscopy, stool for Clostridioides difficle toxin A and B assay, stool for opportunistic organisms with acid-fast staining, and
upper gastrointestinal endoscopy and duodenal biopsy. The tests were unrevealing and
negative. Her colonoscopy was also normal but her colonic biopsy was positive for
cytomegalovirus (CMV) polymerase chain reaction (PCR) (3000 copies CMV deoxyribonucleic
acid [DNA]/25 mg) but the histopathological specimen did not show any evidence of
colitis or inclusions. She underwent a stool multiplex PCR (QIAstat-Dx GIP 2, Qiagen,
Germany), which turned out to be positive for both sapovirus and norovirus GI/GII.
She was treated with a course of nitazoxanide for 1 week and change in immunosuppression
from MMF to azathioprine with resolution in her symptoms. In addition, due to the
presence of high load of CMV DNA in the colonic biopsy she was treated with intravenous
ganciclovir followed by oral valganciclovir.
Case 2
A 48-year-old lady with live unrelated renal transplant in 2014 on triple immunosuppression
with tacrolimus 1.5 mg twice a day, MMF 500 mg twice a day, and prednisolone 5 mg
once daily presented with chronic diarrhea for 6 months and weight loss of 6 kg in
May 2025. She denied any blood in stools or fever. Her stool routine microscopy, stool
for modified acid-fast stain for opportunistic organisms, and stool for C. difficle toxin assay were negative. Her endoscopy revealed some scalloping of duodenal folds
but the biopsy was normal. Her colonoscopy was normal but PCR from biopsy specimen
for CMV DNA showed 400 copies/25 mg and no evidence of colitis or inclusion bodies
on biopsy. Her blood CMV PCR was also negative. Her presenting serum creatinine was
1.99 mg/dL suggestive of acute kidney injury. She was treated conservatively with
intravenous fluid, loperamide, and nitazoxanide along with change in immunosuppression
to enteric-coated mycophenolic acid 360 mg twice a day with improvement in symptoms
and return of serum creatinine to 1.3 mg/dL. She was discharged after improvement
in her symptoms. She was not administered ganciclovir as her CMV DNA load was low
and biopsy or colonoscopy was not suggestive of any evidence of colitis.
Discussion
Diarrhea in post-solid organ transplant recipients is common with the prevalence ranging
from 20 to 50%.[6] Apart from causing distressing symptoms, post-transplant diarrhea is associated
with a risk of causing renal failure, potential medicine toxicity, rejection, and
even mortality.[6] Although infectious causes are more common in the tropics, noninfectious diarrhea
particularly due to immunosuppressive medications is fairly common as well.[1]
[6]
Sapovirus infection is a rare cause of diarrhea in the posttransplant setting.[4] In a large Indian series evaluating 188 samples in posttransplant setting, sapovirus
was isolated in stool PCR in only one patient.[7] In the same series norovirus was the most common cause of posttransplant diarrhea
incriminated in one-fifth of the cases.[7] In our case one of the patients had both norovirus and sapovirus infection, this
dual infection is not uncommon. In fact, in the Indian series evaluating the role
of stool PCR in posttransplant diarrhea, 68% had coinfections.[7]
Norovirus/sapovirus diarrhea is not innocuous and is associated with a greater weight
loss, greater duration of symptoms, and need for immunosuppressive dosage reduction
as compared to bacterial and parasitic causes.[8] It can be associated with acute kidney injury in 80% of the post-renal transplant
cases as in one of our cases.[8] In another large Indian series of 198 post-renal transplant patients, 85 (42.5%)
had diarrhea and majority of these were infective in nature.[9] Among the microbiologically proven infective cases, sapovirus infection was present
in just one case.[9] The same series showed that majority of patients with diarrhea were on MMF and MMF
withdrawal was needed in 48% of these patients in view of persistent or chronic symptoms.
Both of our patients were on MMF, which is a risk factor for developing chronic diarrhea
in the posttransplant setting.[9] In another large prospective multicenter study (DIDACT) evaluating severe diarrhea
in the post-transplant setting, close to 50% of the patients had an infective cause
or nonimmunosuppressive drug-induced diarrhea causing medication as the etiologic
agent.[10] Among the infective causes, bacterial causes including Campylobacter, Salmonella, and C. difficle outnumbered viral causes.[10] However, with the advent of stool multiplex PCR, viral etiologies are being increasingly
recognized.[11]
There is no specific antiviral therapy for sapovirus. Treatment of sapovirus diarrhea
entails fluid repletion and antidiarrheal agents like loperamide to reduce stool frequency.[5] Commonly, a reduction or a change in immunosuppression is required.[5] There have been anecdotal reports of use of nitazoxanide, a well-known anti-protozoal
drug for its use in sapovirus diarrhea due to its purported action of suppression
of intracellular viral replication.[4]
[5] Nitazoxanide is a thiazolide broad-spectrum antiinfective drug against a range of
extracellular and intracellular protozoa, helminths, and bacteria, in addition to
viruses. Nitazoxanide acts by inhibiting pyruvate-ferredoxin oxidoreductase enzyme-dependent
reactions necessary for anaerobic energy metabolism.[12] We used nitazoxanide for 1 week for both of our patients. Since MMF is commonly
incriminated in posttransplant diarrhea, it has been suggested to either use enteric-coated
mycophenolic acid or change immunosuppression to azathioprine to decrease the frequency
of diarrhea as we did for our patients.[5]
[6]
Although both the patients tested positive on the colonic biopsy specimen PCR testing,
none of them demonstrated any evidence of colitis either clinically, on colonoscopy
or histopathology. Demonstration of inclusion bodies is highly specific and immunohistochemistry
remains the gold standard to diagnose CMV colitis.[13] The use of tissue PCR alone for the diagnosis of CMV colitis is controversial since
it does not always connote active infection since CMV DNA can be detected even in
latently infected leukocytes leading to a low positive predictive value of the test.[13] None of our patients had any other evidence of CMV colitis in form of fever, blood
in stools, ulceration on colonoscopy, colitis on biopsy specimen, or presence of classical
intranuclear inclusions. Hence, we cannot firmly incriminate CMV as the cause of diarrhea
in our patients.
Our report indicates that sapovirus is an emerging cause of post-solid organ transplant
diarrhea. (Unpublished data from our center suggest sapovirus infection in 10% post-transplant
patients.) Stool multiplex PCR to detect sapovirus infection is crucial for the appropriate
diagnosis and management of the condition. Future studies should further find out
the prevalence of sapovirus, risk factors, and predictors of successful treatment
among post-renal transplantation patients with chronic diarrhea.
Table 1
Summary of the post-renal transplant patients presenting with sapovirus-induced chronic
diarrhea
|
Details
|
Patient 1
|
Patient 2
|
|
Year of transplant
|
2013
|
2014
|
|
Immunosuppressive medications
|
Tacrolimus (1.5 mg)
MMF (1000 mg)
Prednisolone 5 mg
|
Tacrolimus (3 mg)
MMF (1000 mg)
Prednisolone 5 mg
|
|
Duration of symptoms
|
9 mo
|
6 mo
|
|
Stool routine microscopy
|
Negative
|
Negative
|
|
Stool opportunistic organisms (modified acid-fast staining)
|
Negative
|
Negative
|
|
Stool C. difficle toxin assay
|
Negative
|
Negative
|
|
Stool multiplex PCR
|
Norovirus GI/GII
Sapovirus
|
Sapovirus
|
|
Treatment offered
|
Nitazoxanide, loperamide, and change in immunosuppression to azathioprine
|
Fluids, loperamide, nitazoxanide, and change in immunosuppression to enteric-coated
MPA
|
|
Response to treatment
|
Improvement
|
Improvement
|
Abbreviations: C. difficle, Clostridioides difficle; MMF, mycophenolate mofetil; MPA, mycophenolic acid; PCR, polymerase chain reaction.
