# Retrospective empirical analysis of the success rate of inguinal hernia operations in outpatient and inpatient sectors: a cohort study

## TL;DR

This study analyzes the success rates of outpatient and inpatient inguinal hernia surgeries in Germany from 2014 to 2019, finding limited differences in outcomes and suggesting outpatient care is underused.

## Contribution

The study provides empirical evidence on the effectiveness of outpatient versus inpatient hernia surgeries in Germany, highlighting the underutilization of outpatient care.

## Key findings

- Outpatient surgeries account for less than 20% of inguinal hernia treatments in Germany.
- Inpatient surgeries are associated with fewer reoperations but more complications, though the effect is small.
- Surgical procedure choice has a significant impact on outcomes, while sector choice has minimal influence.

## Abstract

In Germany, the proportion of outpatient surgeries was low during the study period (2014–2019) and low by international standards. Less than 20% of inguinal hernias are treated on an outpatient basis. Hybrid DRGs are intended to promote outpatient treatment, but their impact on the quality of care and referral criteria has not been sufficiently investigated empirically.

A retrospective analysis of routine data included 90,512 cases from 41 company health insurance funds, spanning 2014 to 2019. These were analysed descriptively in terms of care sector, age, and surgical procedure, as well as through two logistic regressions on reoperations and complications, including interaction effects.

The proportion of outpatient surgeries is already below 40 % in adults and continues to decline with increasing age. The choice of procedure differs significantly between sectors. The regressions explain only 3.3 % and 4 % of the variance, respectively, meaning that the variables have only a minor impact on the success of the surgery. Inpatient surgeries are associated with fewer reoperations and more complications, although the absolute effect size is small. The surgical procedures have a significant influence. There are no relevant interaction effects between the choice of sector and the other variables.

A sector-specific allocation based on the analysed parameters cannot be justified based on evidence. Since inpatient procedures do not show consistent superiority, there is no medical advantage over outpatient procedures. A cost-adjusted design of hybrid DRGs appears necessary to enable indication-appropriate procedure selection and to avoid potential misguided incentives that compromise the quality of care.