Down syndrome (DS) is the most frequent chromosomal abnormality associated with Hirschsprung's disease (HD). It has often been suggested that this association results in poorer outcomes with regard to postoperative complications, continence and mortality. On the other hand, the results after surgical treatment of HD in patients with DS are reportedly similar to those in cases with HD alone. The objective of this study was to determine the incidence of DS in cohorts with HD, and to compare pre-/postoperative complications, functional outcome and mortality between cohorts with and without coexisting DS. A systematic literature-based search for relevant cohorts was conducted using multiple online databases. The number of DS cases in HD cohorts was recorded and data on pre-/postoperative complications, functional outcome and mortality were extracted. Pooled odds ratios with 95 % confidence intervals were calculated using meta-analysis methodology. Sixty-one articles met defined inclusion criteria, comprising data from 16,497 patients with HD. The overall incidence of DS among them was 7.32 %. Vice versa, the incidence of HD in 29,418 patients with DS was 2.62 %. There were no significant differences regarding the male-to-female ratio between cohorts with and without coexisting DS (4:1 vs. 3:1 respectively; P = 0.5376). The rate of additional comorbidities was significantly higher in HD associated with DS (P < 0.0001). Recto-sigmoid HD was in both cohorts the most common type of HD (P = 0.8231). Long-segment HD was significantly more frequent in HD with coexisting DS (P = 0.0267), while total colonic aganglionosis occurred significantly more often in HD without DS (P = 0.0003). There were no significant differences in preoperative constipation/obstruction (P = 0.5967), but the rate of preoperative enterocolitis was significantly higher in HD associated with DS (P = 0.0486). Postoperative complications such as recurrent enterocolitis (P = 0.0112) and soiling (P = 0.0002) were significantly more frequent in HD with coexisting DS. Although not statistically significant, fecal incontinence (P = 0.1014) and persistent constipation (P = 0.1670) occurred more often after surgical treatment of HD with DS. The mortality rate was significantly higher in HD associated with DS (P < 0.0001). The association of HD with DS is well-recognized with an incidence of 7.32 %. A large number of patients with DS continue to have persistent bowel dysfunction after surgical treatment of HD. Our data provide strong evidence that the coexistence of HD and DS is associated with higher rates of pre-/postoperative enterocolitis, poorer functional outcomes and increased mortality.
