Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome (MMIHS): A Case Presentation.

Carmen R. Duque, MSN, APRN, PNP-BC; Raquel Pasarón, DNP, APRN, FNP-BC; Juan L. Calisto, MD Nicklaus Children’s Hospital, Miami, Florida

IntroductionMegacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is a rare genetic disorder categorized by a dysfunction of the smooth muscles which affects the intestine and the bladder. Presenting symptoms include megacystis described as bladder distension in the absence of mechanical obstruction, microcolon, and intestinal hypoperistalsis/dysmotility.

MMIHS may be suspected during the second trimester ultrasound with findings of bladder enlargement with or without hydroureteronephrosis and normal or increased amniotic fluid volumes.

Newborn may present with symptoms of: • Gastrointestinal and bladder obstruction• Abdominal distension/pain, bilious emesis, failure to pass meconium• Inability to pass urine, and absent or decreased bowel sounds

Initial radiologic studies may show:• Dilated loops of bowel with opacity of distal gas• Dilated stomach, and small intestines with associated malrotation• Urologic findings include distended bladder with large capacity,

hydroureteronephrosis, and vesicoureteral reflux (VUR)

Differential diagnosis of MMIHS include:• Hirschsprung disease• Lower urinary tract obstruction• Small bowel atresia or colonic atresia

• Meconium ileus/plug• Anorectal malformation

Case Presentation

O.V. is a 3-month-old male who initially presented to the ED with a 3-day history of constipation associated with severe abdominal distension concerning for obstruction. Pediatric surgery was consulted for further evaluation.

Past Medical History:• Born at 37 weeks’ gestation• First bowel movement at 36 hours of life. Since birth he had mucoid yellow

stools every 2 to 3 days and was followed by his pediatrician for colic • Prenatal US reporting an echogenic bowel and a distended bladder • At 2 months of age the family relocates to seek specialized care in a larger

pediatric institution

• Patient develops projectile vomiting and is referred to Gastroenterology (GI) and Urology at an outside institution

• At 3 months of age undergoes a cystoscopy and vesicostomy for distended bladder

• Patient was referred to Genetics for evaluation of MMIHS• Mother reported anorectal malformation and Hirshsprung disease

was ruled out by GI

Physical Exam:• Severely distended abdomen, tympanic, with hypoactive bowel sounds• Lungs clear• Vitals WNL• Vesicostomy draining clear yellow urine

• Digital rectal exam with positive squirt sign • KUB: Significant dilated loops of bowel

concerning for bowel obstruction, possible Hirschsprung enterocolitis

Initial Treatment:• Rectal irrigations were performed in the emergency department with explosive stool output • Admission to pediatric/ colorectal surgical service• Consult with Urology, GI, and Genetics

Treatment and Work-up:• Patient started on rectal irrigations every 6 hours• Flagyl • IVF/ NPO• Renal/ bladder US

• Initiated work-up for Hirschsprung disease• Contrast enema• Laboratories• Rectal biopsy • Genetic evaluation and mutation analysis

Diagnosis:• Barium Enema: Small caliber rectosigmoid colon with suspected transition

at the distal colon and proximal sigmoid colon. Abnormal colonic distention proximal to the transition zone suspicious for Hirschsprung disease

• Renal/Bladder US: Mild left pelviectasis. Normal kidneys• DMSA Renal Scan: Normal• Rectal biopsy confirms presence of ganglion cells• Genetic testing for MMIHS confirmed diagnosis

• Surgical management:• Broviac for long term TPN – patient unable to tolerate feeds• GT for enteral nutrition• Diverting colostomy• Vesicostomy (performed at outside hospital)• Patient referred to pediatric center with specialists in MMIHS

Objectives1. Participants will be able to identify clinical characteristics of MMIHS.

2. Participants will recognize key elements in diagnosing MMIHS prenatally and postnatally.

3. Participants will be able to describe treatment and management of MMIHS. References• Ambartsumyan, L. (2019, May 09). Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome overview. Retrieved August 25, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK540960/• De Sousa, J., Upadhyay, V., & Stone, P. (2016). Megacystis microcolon intestinal hypoperistalsis syndrome: Case reports and discussion of the literature. Fetal Diagnosis & Therapy, 39(2), 152–157. https://doi-org.ezproxy.fiu.edu/10.1159/000442050

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Conclusion• MMIHS is a rare genetic disorder associated with significant morbidity and mortality. • Caused by mutations in the ACT2 gene and is inherited in an autosomal dominant manner.

However, many cases of MMIHS are caused by de novo mutations • Characterized by megacystis (bladder distension in the absence of mechanical obstruction),

microcolon, and intestinal hypoperistalsis (dysmotility) • Suspected prenatally secondary to findings of fetal megacystis on prenatal ultrasound• Affected infants present at birth with symptoms of bowel and bladder obstruction • Other symptoms include bilious emesis, failure to pass meconium, and inability to

spontaneously void needing catheterization • Gastrointestinal complications include: • Microcolon • Intestinal dysmotility

• Malrotation and complications such as short bowel syndrome and recurrent chronic intestinal pseudo-obstruction (CIPO)

• Urologic complications include: • Myopathic dysfunction of bladder • Febrile urinary tract infections

• Vesicoureteral reflux (VUR) • Hydronephrosis

• Intestinal dysfunction can lead to • Nutritional compromise and intestinal failure resulting in dependence on total

parenteral nutrition (TPN)• Individuals may develop complications from the TPN including central line infections, liver

dysfunction, and liver failure • Multivisceral or isolated intestinal transplantation are sometimes considered

Key Points• Early identification is crucial in developing the appropriate surgical plan of care. • Associated urologic, gastrointestinal, genetic, cardiac, and other comorbidities must

be diagnosed early to prevent unnecessary surgery, preserve renal function, maintain appropriate nutritional status, avoid hepatic complications, and prevent chronic infections.

• Prognosis may be poor due to associated complications from TPN, recurrent surgeries, sepsis, malnutrition, and possible multiorgan failure.

• Children with MMIHS require a multidisciplinary management with specialists in pediatric gastroenterology, urology, nutrition, pediatric surgery, genetics, and rehabilitative therapies among others. Individualized surveillance should be performed using a multidisciplinary approach. Further treatment may include multivisceral transplantation as an alternative to children who cannot tolerate total parenteral nutrition.