Meconium obstruction in absence of cystic fibrosis in low birth weight infants: an emerging challenge from increasing survival
Authors: Paradiso Valentina Filomena , Briganti Vito , Oriolo Lucia , Coletta Riccardo , Calisti Alessandro 
Published: November 2011

Abstract

Background
Meconium abnormalities are characterized by a wide spectrum of severity, from the meconium plug syndrome to the complicated meconium ileus associated with cystic fibrosis. Meconium Related Ileus in absence of Cystic Fibrosis includes a combination of highly viscid meconium and poor intestinal motility, low grade obstruction, benign systemic and abdominal examination, distended loops without air fluid levels. Associated risk factors are severe prematurity and low birth weight, Caesarean delivery, Maternal MgSO4 therapy, maternal diabetes. In the last 20 yrs a new specific type of these meconium related obstructions has been described in premature neonates with low birth weight. Its incidence has shown to increase while its management continues to be challenging and controversial for the risk of complicated obstruction and perforation.

Materials and methods
Among 55 newborns admitted between 1992-2008 with Meconium Related Ileus as final diagnosis, data about Low Birth Weight infants (LBW < 1500 g) were extracted and compared to those of patients ≥ 1500 g. Hischsprung's Diseases and Cystic Fibrosis were excluded by rectal biopsy and genetic probe before discharge. A softening enema with Gastrografin was the first option whenever overt perforation was not present. Temporary stoma or trans appendiceal bowel irrigation were elected after unsuccessful enema while prompt surgical exploration was performed in perforated cases. NEC was excluded in all operated cases. Data collected were perinatal history and neonatal clinical data, radiological signs, clinical course and complications, management and outcome.

Results
30 cases with BW ≥ 1500 g had an M/F ratio16/14, Mean B.W. 3052 g, Mean G.A. 37 w Caesarean section rate 40%. There were 10 meconium plug syndrome, 4 small left colon syndromes, and 16 meconium ileus without Cystic Fibrosis. Five cases were born at our institution (inborn) versus 25 referred after a mean of 2, 4 Days (1-7) after birth in another Hospital (outborn). They were managed, after a Gastrografin enema with 90% success rate, by 1 temporary Ileostomy and 2 trans appendiceal irrigation. 25 cases with BW< 1500 g (LBW) had M/F ratio 11/14, Mean B.W. 818 g, Mean G.A. 27 w, Caesarean section rate 70%, assisted ventilation 16/25. There were 8 inborn and 17 outborn. Gastrografin enema was successful in 6 out 8 inborn infants only, all referred within one week from birth. There were 12 perforations mainly among late referred LBW outborn.

Conclusions
Meconium Related Ileus without Cystic Fibrosis responds to conservative management and softening enema in most of mature infants. In LBW clinical course is initially benign but as any long standing bowel obstruction management may present particular challenges. Clinical and plain radiographic criteria are reliable for making diagnosis and testing for Cystic Fibrosis may not be indicated. Enema may be resolutive when performed in a proper environment. Perforated cases may be confused with NEC which is excluded by clinical history, no signs of sepsis, lab signs missing, abdominal signs missing, typical radiological signs missing. The higher complication rate is recorded among cases delivered and initially managed in Neonatal Units without co-located Surgical Facilities. Early diagnosis and aggressive medical therapy may lead to higher success rate and help avoiding surgical interventions. Surgical therapy in uncomplicated cases, unresponsive to medical management, should be minimally aggressive.