A systematic review and meta-analysis of risk factors and treatment choices in emphysematous pyelonephritis

Purpose: Emphysematous pyelonephritis (EPN) is an acute, severe necrotising infection of the kidney. There has been a shift from early nephrectomy to conservative methods. We conducted a meta-analysis to assess the impact of risk factors and treatment choices on outcomes in EPN.

Methods: We conducted a database search of all studies in English, reporting more than 12 patients of EPN from 1980 to 2020. We compiled the demographics, clinical presentations, risk factors, critical diagnostic results, treatment modalities and outcomes, including mortality.

Results: We identified 37 observational studies, 32 retrospective and 5 prospective. The studies reported on 1146 patients, of which 790(68.9%) were female, and 946 (82.5%) were diabetic. In addition, 184 (16.1%) patients had stones, and 235 (20.5%) had obstructive uropathy. Fever and flank pain were the most frequent symptoms. The most common clinical features were pyuria, fever, flank tenderness, and tachycardia. E. coli, Klebsiella pneumoniae and Proteus were the most frequent organisms isolated. X-ray KUB and ultrasound were used as initial diagnostic modalities, but CT scan was the usual diagnostic and confirmatory investigation. Confusion, shock, thrombocytopenia, sepsis, emergency nephrectomy and hyponatremia were significantly associated with mortality. In particular, confusion and hyponatremia were associated with a sevenfold increase in mortality risk. There was no evidence that diabetes, stones, obstructive uropathy, AKI or proteinuria was associated with higher mortality. Nevertheless, 143 of the total 1146 patients died (12.5%). While 26% of the patients who had upfront emergency nephrectomy died, only 9.7% and 10% of patients with medical management and medical management plus minimally invasive treatments died. However, patients that failed medical and minimally invasive treatments and needed salvage emergency nephrectomy had a mortality of upwards of 27%.

Conclusion: The risk factors for mortality in emphysematous pyelonephritis are shock, thrombocytopenia, confusion, hyponatremia and emergency nephrectomy. Conservative and minimally invasive treatment should be the initial management strategy for emphysematous pyelonephritis as they carry lesser mortality risks. The presence of risk factors may help predict the subset of patients who need aggressive treatment and minimally invasive treatment modalities or early nephrectomy.