Clinical History
Elderly woman with history of hysterectomy, chronic ischemic heart disease and cardiac pacemaker, and chronic renal failure treated with long-term ambulatory peritoneal dialysis (PD).
Presents to emergency department complaining of vomiting, diarrhoea, upper central abdominal pain since three days.
Physically found afebrile, with distended diffusely tender abdomen, absent peritonism.
Imaging Findings
Laboratory revaled leukocytosis, elevated (74 mg/L) C-reactive protein. Estimated glomerular filtration rate was <10 ml/min. Inspection at the PD exit site excluded abnormal discharge. After ultrasound (not shown) depicted hypo-anechoic tracking along the catheter, the nephrologist opted for removal.
Multidetector CT (Fig.1) was requested to investigate suspected tunnel and/or peritoneal infection, and to decide between catheter repositioning or PD discontinuation. CT showed a midline infraumbilical abscess centered in and coursing through the anterior abdominal wall, with spared superficial subcutaneous fat and overlying skin, consistent with diagnosis of tunnel infection. Additionally, some peritoneal calcifications suggestive of early sclerosing encapsulating peritonitis were noted. The kidneys' appearance was consistent with chronic kidney failure.
Effluent abnormalities and CT signs (serosal thickening and hyperenhancement, mesenterial inflammation, small bowel mural thickening) indicating bacterial peritonitis were absent.
Surgical toilette (postoperative CT status in Fig.2) and cultures confirmed tunnel infection from Enterobacter cloacae. The patient started haemodialysis and recovered after prolonged hospitalization.
Discussion
Peritoneal dialysis (PD) is a viable first-line modality for renal replacement therapy, which is used in one-third of new end-stage renal failure cases and in 11% of dialysis patients overall. PD is preferred in people with diabetes, impaired cardiac function, difficult vascular access, and may be performed either manually (continuous ambulatory PD) or using mechanical devices (automated PD). Compared with haemodialysis, PD is cheaper, does not need skilled personnel and anticoagulation, allows patients more daily freedom, and offers equivalent survival. PD uses the natural semipermeable serosal membrane to filter blood and dialysate solution infusion into the peritoneal cavity via an indwelling catheter entering through the anterior abdominal wall and with its tip in the pelvis [1].
Unfortunately, the long-term effectiveness of PD is limited by complications including infections, catheter dysfunction, dialysate leaks, hernias and encapsulating sclerosing peritonitis in descending order of frequency. Collectively, bacterial catheter-related infections (CRIs) and peritonitis occur once every 20-30 months per patient. Caused by a variety of organisms including the worrisome S.aureus and Pseudomonas, CRIs account for 39% of catheter removals and are associated with increased risk (20% incidence) of peritonitis. Among CRIs, exit-site infections (ESIs) are heralded by purulent discharge with or without erythema at the catheter-epidermal interface, and are amenable to topical therapy. Conversely, tunnel infections (TIs) develop in the subcutaneous and intramuscular catheter track, may be clinically occult or manifest with abdominal wall oedema and tenderness, are less likely to resolve with conservative treatment and require prompt catheter removal [1-5].
The established clinical guidelines recommend imaging of CRIs to decide on duration of antibiotics, device removal and surgical tunnel revision. Ultrasound may promptly identify hypo-anechoic bands consistent with CRI surrounding the tube, or abscess collections in the abdominal wall or peritoneal cavity [1, 2]. As this case exemplifies, multidetector CT comprehensively evaluates possible PD-related complications: TIs appear with the characteristic abscess appearance including hypodense content and peripheral enhancing rim along the catheter track through subcutaneous fat, abdominal wall muscles and parietal peritoneum. Intravenous use of iodinated contrast medium should be balanced with its potential nephrotoxicity in patients with residual renal function. Furthermore, CT serves to differentiate infections of the extraperitoneal structures of the abdominal wall from bacterial peritonitis: the latter manifests with abdominal pain, “cloudy” effluent rich in leukocytes, and represents the leading cause of hospitalization, discontinuation to haemodialysis, and mortality (3.5-10%) in PD [1-3, 6, 7].
Differential Diagnosis List
Abdominal wall tunnel infection complicating peritoneal dialysis
Catheter exit site infection
Bacterial peritonitis
Tubercular peritonitis
Small bowel obstruction from adhesions
Final Diagnosis
Abdominal wall tunnel infection complicating peritoneal dialysis
