The Role of Peritoneal Scintigraphy in the Detection of Continuous Ambulatory Peritoneal Dialysis Complications

Abstract

While continuous ambulatory peritoneal dialysis (CAPD) offers several advantages over hemodialysis in patients with end-stage renal disease, several complications have been recognized. The intraperitoneal instillation of dialysate increases intra-abdominal pressure and consequently predisposes the patient to leaks and herniations through defects in the abdominal wall.

The use of an intraperitoneal radiolabeled colloid has been previously described to image entities such as hernias, patent processus vaginalis, abdominal wall, and diaphragmatic leakage. This study shows a simple, non-invasive method of determining the site of dialysate leak and its importance to assist further patient management.

There has been a continuing increase in the number of end stage renal disease patients maintained on chronic peritoneal dialysis (CPD). Many patients choose CPD as their preferred chronic dialysis treatment, though approximately 20% of patients who drop out transfer to hemodialysis annually.¹ Although peritonitis remains the major reason for transfer to hemodialysis, other factors such as exit site infections, catheter-related problems, abdominal wall and inguinal hernias, loss of ultrafiltrations, and poor clearance contribute to CPD technique failure.² In order to permit the continuation of long-term therapy with CPD, these complications should be resolved.

Routine laboratory evaluation or physical examination can detect some CPD-related problems; however, some patients require more complicated investigations to evaluate their problems properly.

Keywords:

• peritoneal scintigraphy
• CAPD
• end stage renal disease

MATERIALS AND METHOD

Between 2000–2004, 17 patients with varying complaints from the Nephrology unit were referred for peritoneal scintigraphy (nine females and eight males, ranging in age from 20–75 years). The duration of CAPD ranged from 1–87 months (mean duration 25.5 months), and the mean age of the patients was 42.26 years. Prior to the scintigraphic study, the abdominal cavity of the patients was drained of all dialysis solution in the nuclear medicine department. After completing the drainage, the patient was placed supine under the gamma camera to allow a full view of the abdomen and lung bases. Multi-view planar imaging was performed with a dual-head gamma camera (ADAC-VERTEX with LEHR collimator and full matrix size). The energy window was set at the 140 keV photopeak with a 20% window. The scintigraphic study was initiated by mixing 2.0 mCi of 99m-technetium sulfur colloid in two liters of 1.5% dextrose peritoneal dialysis solution and then administered rapidly into the peritoneal cavity through the abdominal catheter. Distribution of the fluid was monitored while the patient was in the supine position. During the installation phase, dynamic images of the abdomen were obtained, one frame per minute for the first 15 minutes. Immediately after the infusion was completed, post-infusion images (five minutes per view) were obtained in the anterior-posterior, lateral, and (if necessary) oblique projections. The patients were then encouraged to walk for 10–15 minutes. Non-ambulatory patients were asked to roll from side to side while on the imaging table to promote the intraperitoneal mixing of the radiotracer. Post-ambulatory static images were taken at the same position (anterior-posterior, lateral, and oblique). After these images were obtained, the peritoneal cavity was drained. Following the drainage, a third set of post-drainage static images were obtained (five minute per view). Late images were acquired in some patients up to 24 hours, if the clinical suspicions were present for dialysate leakage.

The images were interpreted by two nuclear medicine physicians. The patients' results were followed-up with Nephrology unit.

RESULTS

The patients were evaluated in four groups according to their symptoms:

1. Group 1: patients with abdominal wall swelling (n: 5, M: 1, F: 4; age range: 23–75; mean duration of CAPD: 10.2 months).

2. Group 2: patients with inguinal or genital swelling (n: 5, M: 4, F: 1; age range: 23–54; mean duration of CAPD: 39.2 months).

3. Group 3: patients with pleural effusion (n: 3, M: 1, F: 2; age range: 25–34; mean duration of CAPD: 28 months).

4. Group 4: control group (n: 4, M: 2, F: 2; age range: 44–59).

Group 1: Abdominal Swelling

There were five patients in this group who were referred for abdominal wall swelling. In four of them, peritoneal scintigraphy was positive. In one patient, there was pericatheter leakage on the images that remained up to 24 hours (see Figure 1), and this patient was treated successfully with increased ultrafiltration. In two of the other four patients, their scans demonstrated a leak of dialysate in the right superior and inferior quadrant of abdominal region, respectively. In these patients, obesity and steroid use were the risk factors for complications.[1] One of these patients did not respond to ultrafiltration changing and transferred to hemodialysis. The other patient was 75-years-old and obese, and had died soon thereafter. One patient, who had a known umbilical hernia, had a focal area of intense concentration of activity at the midline of the abdominal wall (see Figure 2). The last patient was 51-years-old and was referred with abdominal swelling. His MR images showed suspicious areas of abscess formation in the anterior of left psoas muscle. Transudative fluid was drained from this region. This was thought to be due to the peritoneal leakage, and the patient was referred for scintigraphy; however, no abnormal accumulation of radiotracer was observed in the abdomen. There was no activity on 24 hour-images.

Figure 1 Early, delayed, and 24-hour images of a patient who had pericatheter activity accumulation (leakage) on the images. Anterior 10 min image shows pericatheter activity accumulation on the right lower abdominal wall, at the entry of the catheter. A lateral image confirms that the activity is around the catheter and remains at 24 hour image.

Figure 2 Anterior and left anterior oblique (LAO) images of a patient at 10 min, post-drainage phase and 24-hour. This patient had a previously known umbilical hernia. Post-drainage and 24-hour images show two foci of intense activity at the midline of the abdominal wall.

Group 2: Genital Edema

All patients of this group had genital and/or inguinal edema. In two of five patients, the presence of inguinal hernia was revealed. One of these patients was a 42-year-old male with right genital edema. His scan demonstrated increased activity in right inguinal canal (see Figure 3). This patient had left inguinal hernia operation previously, which was reflected in the predisposing factors for complications. Another patient was a 23-year-old, and his scintigraphy showed intense activity accumulation extending to left scrotal region in early and delayed 24 hours images. There was no significant predisposing factor for this patient. However, in these two patients, the duration of CAPD was considerably longer than the first group. The other two patients' scans were free of dialysate leakage, but there was loculation of fluid collection on the anterior abdominal wall. These two patients were treated successfully by changing CAPD to a Nightly Intermittent Peritoneal Dialysis program. The remaining patient's scan was normal. This patient was required to transfer to hemodialysis for one year, and then he successfully restarted CAPD therapy.

Figure 3 Patient referred with right genital edema. Post-drainage and delayed images of lower abdomen show increased linear activity in right inguinal canal.

Group 3: Pleural-Peritoneal Leakage

The clinical indication of these patients for peritoneal scintigraphy was an evaluation of pleural-peritoneal leakage. All patients had negative findings for pleural-peritoneal leakage. One of these patients was diagnosed with tuberculosis. The second patient was temporarily transferred to hemodialysis and started on CAPD therapy.

Group 4: Control Group

These scans were taken for defining the normal distribution of radiotracer activity.

DISCUSSION

CAPD is preferred over hemodialysis for patients in whom vascular access is difficult or for those with cardiovascular disease. In addition many patients choose CAPD because it allows more mobility.[3] Complications are more frequent with CAPD than hemodialysis; however, CAPD has a number of pathophysiologic factors that may contribute to the formation of hernias and leakage from the peritoneal cavity. These factors are induced by intraabdominal pressure, resulting in increased stress on the abdominal wall and diaphragm.[4],[5] In addition, local predisposing factors include complete or partially opened processus vaginalis and prior abdominal surgery, including hernia repair. Some systemic conditions of end stage renal failures, including uremia, obesity, transperitoneal protein loss, and anemia, also contribute these problems. Extraperitoneal leakage of dialysate may occur at the catheter site as well as from tears in the peritoneum within hernia sac.[6],[7] These clinical situations can cause different clinical symptoms, such as scrotal edema, penile edema, edema of the abdominal wall, or a pleuro-peritoneal leak. A number of different diagnostic procedures have been employed to determine the reason of these complications. These procedures include peritoneal scintigraphy, computerized tomography (CT) with intraperitoneal contrast, and MR peritoneography. CT peritoneography has several limitations involving multiplanar imaging capabilities, and, in addition, iodinated contrast material is required, which runs the risk of anaphylactic reactions.[8] Also, MR, while extremely rare, has some contrast agent-related side effect risk.

For the evaluation of CAPD complications, peritoneal scintigraphy is a simple, non-invasive method especially for determining the site of dialysate leakage, and it is important in assisting further patient management. Another advantage of scintigraphic imaging is that it allows monitoring the patients for several hours following the installation of the labeled dialysate. This capability is important because scintigrams that were initially negative often becomes positive after several hours of ambulation. Post-drainage images were also helpful in confirming extraperitoneal leakage. Beside these advantages, the technique of scintigraphy is safe, with low radiation exposure.

There is little literature regarding the use of peritoneal scintigraphy in the detection of CAPD complications. The largest is Juergensen et al's study of 48 patients with CAPD.[1] They found peritoneal scintigraphy very useful, particularly in patients who present with inguinal or scrotal swelling caused by hernia leaks and who would benefit from surgical intervention. In addition, in patients with poor dialysis drainage and/or impaired ultrafiltration, the scintigraphic finding might help to clarify the etiology and direct the appropriate intervention.

Another interesting approach was to evaluate CAPD patients with peritoneal scintigraphy who had no apparent complications.[9],[10] In one study,[9] scintigraphically detectable subclinical structural defects involving the inguinal canal or abdominal wall were present in 29% of 48 patients. Within five months, four of these defects progressed to clinically significant CAPD-related structural complications. In another study (n = 59),[10] among the patients without obvious abdominal hernia symptoms, 17% positive abdominal hernia cases were discovered by scintigraphy.

The incidence of dialysate leakage is greater than 5% in CAPD patients, which represents a major noninfectious complication of peritoneal dialysis. In fact, this percentage probably underestimates the number of early leaks. Early leak most often manifests as a pericatheter leak, while late leaks tend to develop during the first year of CAPD.[11] Late leaks may present more subtly with subcutaneous swelling and edema, weight gain, peripheral or genital edema, and apparent ultrafiltration failure. In this study, among Group 1 patients who presented with abdominal wall swelling and edema, the development of leak had a mean duration of 10.2 months. The results also showed that the occurrence of genital edema duration was longer that in Group 1 patients (mean 39.2 months and 10.2 months, respectively). In one patient with genital edema, peritoneal scintigraphy was negative for inguinal leakage but there was loculation of fluid collection on the anterior abdominal wall. This patient has been treated with CAPD for six months and had no complaints of abdominal swelling. In this patient with no symptoms, the abdominal pathology observed by scintigraphy can progress to a symptomatic stage over time, as previously mentioned. In this patient, peritoneal scintigraphy was probably useful in detecting the complication earlier.

A limitation of this study is that the false negative diagnoses cannot be determined because definitive surgical proof was not obtained in any patient. The long-term follow-up of patients was the only support of the findings and results.

In conclusion, peritoneal scintigraphy is a cheap, safe, and non-invasive diagnostic tool in the management of complications of CAPD. It may be very useful in detecting complications in patients without clinical evidence of complications but who may have predisposing factors for possible abdominal hernias.