Pleural effusion in patient in continuous ambulatory peritoneal dialysis (CAPD)

Clinical History

Patient with end-stage renal disease treated with CAPD for the past 6 months. She complained of dyspnoea after every peritoneal dialysis session because of a right pleural effusion. Cardiac, infectious and malignant causes were ruled out. Pleural effusion analysis revealed a transudate with a glucose concentration higher than serum glucose concentration.

Imaging Findings

Contrast-enhanced CT of the chest detected a right pleural effusion but ruled out diaphragmatic hernias as well as pleural or pulmonary masses (Fig. 1). CT-peritoneography was undertaken after injection of contrast medium (300 mg I/kg) mixed to the dialysate through the peritoneal catheter; the procedure was performed by a nurse of the nephrologic unit. The patient was invited to walk and to strain after the injection of the contrast-enhanced dialysate. Scans of the thorax and the abdomen were acquired 2 hours later; CT-peritoneography demonstrated a contrast-enhanced right pleural effusion with a density slightly less than peritoneal contrast-enhanced fluid (218 HU, SD 19 versus 218 HU SD 18) (Fig. 2a). No diaphragmatic defects nor hernias were evident. The dialysate was equally distributed within the peritoneal space; CT ruled out entrapment of the peritoneal catheter, abdominal hernias, or other abdominal leakages (Fig. 2b, c; Fig. 3).

Discussion

CAPD, when clinically suitable, has become a widespread method to treat subjects with end-stage renal disease, because it guarantees better cost-effectiveness and greater patient autonomy than haemodialysis. Unfortunately effectiveness of CAPD is hampered by long-term complications, among which infections are predominant. On the other hand non-infectious complications (i.e. catheter displacement or entrapment, peritoneal hernias, dialysate leakage) decrease the drainage of the dialysate and the efficacy of CAPD [1].
Rupture of peritoneal synovia results in leakage of dialysate into extraperitoneal spaces or in a pleural cavity, more frequently on the right side [1]. Similarly to peritoneal herniation, leakage is due to increase of intra-abdominal pressure, which reaches the highest values during straining and coughing, and results in fluid retention and poor dialysate drainage [1, 2]. Dialysate leakage affects up to 5% of patients with CAPD and is related to surgical technique, interval time between catheter insertion and beginning of CAPD, abdominal wall weakness (from obesity, steroid use, previous surgery) or chronic lung disease [1].
Acute hydrothorax complicates 1.6% of CAPD in adults and usually occurs on the right side [3]. The mechanism is not clearly understood, and a hypothesis is suggested that fluid passes into the pleural cavity through a congenital or acquired diaphragmatic defect, or via diaphragmatic lymphatics or because of the peritoneal-pleural pressure gradient [3, 4].
Multidetector CT-peritoneography with multiplanar reformations is useful to delineate anatomy of the diaphragm and its defects appearing as a peritoneal contrast-filled bleb-like lesion [4, 5].
However, since most of diaphragmatic defects are microscopic and very difficult to identify also during video-assisted thoracoscopy or autopsy, CT can fail to visualize a diaphragmatic defect but can demonstrate a passage of the contrast-enhanced dialysate from the peritoneal cavity into the pleural space, as in the present case [3].
MRI can be alternative to CT for detecting CAPD complications. Multiplanar T1-weighted and T2-weighted fat-suppressed images should be acquired using the dialysate alone as contrast medium. Instillation of gadolinium contrast agents should be avoided for risk of nephrogenic systemic fibrosis in patients with renal insufficiency [1]. Because of the higher cost of examinations and restricted availability of equipment, MR-peritoneography should be firstly indicated for patients more sensitive to radiation dose accumulation, such as the paediatric population.
Take home message:
- Pleural leakage, although rare, impairs effectiveness of CAPD.
- CT-peritoneography is the preferable method to demonstrate a pleural leakage in patients treated with CAPD.

Differential Diagnosis List

Final Diagnosis

Pleural effusion complicating peritoneal dialysis

URL:	https://www.eurorad.org/case/11626
DOI:	10.1594/EURORAD/CASE.11626
ISSN:	1563-4086