Frequent involvement of the internal cuff segment in CAPD peritonitis and exit-site infection - an ultrasound study

Tunnel ultrasound can guide the use of peritoneal dialysis catheter exit site relocation by external splicing and cuff removal in refractory tunnel infection

BACKGROUND

Peritoneal dialysis (PD) catheter related infections continue to be a major cause of morbidity and transfer to hemodialysis (HD) in PD patients. The treatment of tunnel infection (TI) could be challenging, especially when the infection involves the superficial cuff requiring the removal of the catheter. To spare the patient the loss of the catheter and the transfer to HD, several mini-invasive surgical techniques have been proposed as rescue therapy. Furthermore, nowadays, the rapid growth of digital technology has enormously increased the diagnostic sensibility of the echo signal allowing to accurately defines the extent of the infectious process along the PD catheter tunnel.

METHODS

Between 1st January 2020 and 31st December 2021 seven patients who underwent exit-site relocation by external splicing and cuff removal at our institution due to refractory TI were included in the study. All patients were followed until 12 months after the procedure. As soon as TI was defined refractory to the medical therapy, an ultrasonographic examination of the catheter tunnel was performed to define the extent of the infectious episode.

RESULTS

Among the 7 infectious episodes, 4 were caused by P. aeruginosa, and 3 by S. aureus. Around the superficial cuff the hypo/anechoic collections detected by ultrasounds showed a mean diameter of 3.05 ± 0.79 mm. The exit-site relocation by external splicing and cuff removal was successful in all cases (7/7, 100%).

CONCLUSIONS

In our experience the use of exit site relocation by external splicing and cuff removal as rescue therapy for TI with positive ultrasounds for TI limited to superficial cuff involvement and without secondary peritonitis, yielded to promising results with a success rate of 100%. This preliminary experience underlines the paramount usefulness of tunnel echography in accurately defining the extent of TI and, consequently, guiding the choice of the therapeutical approach in refractory TI.

Utility of ultrasonographic examination in catheter-related infections in peritoneal dialysis: a clinical approach

Peritoneal dialysis- (PD) related infections continue to be a major cause of morbidity and mortality in patients on renal replacement therapy via PD. However, despite the great efforts in the prevention of PD-related infectious episodes, approximately one third of technical failures are still caused by peritonitis. Recent studies support the theory that ascribes to exit-site and tunnel infections a direct role in causing peritonitis. Hence, prompt exit site infection/tunnel infection diagnosis would allow the timely start of the most appropriate treatment, thereby decreasing the potential complications and enhancing technique survival. Ultrasound examination is a simple, rapid, non-invasive and widely available procedure for tunnel evaluation in PD catheter-related infections. In case of an exit site infection, ultrasound examination has greater sensitivity in diagnosing simultaneous tunnel infection compared to the physical exam alone. This allows distinguishing the exit site infection, which will likely respond to antibiotic therapy, from infections that are likely to be refractory to medical therapy. In case of a tunnel infection, the ultrasound allows localizing the catheter portion involved in the infectious process, thus providing significant prognostic information. In addition, ultrasound performed after two weeks of antibiotic administration allows monitoring patient response to therapy. However, there is no evidence of the usefulness of ultrasound examination as a screening tool for the early diagnosis of tunnel infections in asymptomatic PD patients.

Contrast-enhanced ultrasound in peritoneal dialysis: when and how to perform it

In the field of peritoneal dialysis contrast enhanced ultrasound (CEUS) is a new add-on examination to B-mode ultrasound, but until recently it has never been systematically studied. Based on the experience of the Project Group "Integrated Imaging and Interventional Nephrology" of the Italian Society of Nephrology, CEUS is helpful for evaluating catheter malfunction, peritoneal-pleural communication, leakage, and herniation, and in particular it facilitates dynamic functional imaging of the catheter and its complications. The use of CEUS in peritoneal dialysis is simple, repeatable, safe, radiation-free, and appears to be less time-consuming and more cost-effective than other radiological imaging techniques such as peritoneography, computed tomography, magnetic resonance or peritoneal scintigraphy.

The Underrated Role of Ultrasound in Peritoneal Dialysis

Ultrasound is very effective in performing procedures and assessment of complications in peritoneal dialysis. The ultrasound examination can be applied for preoperative assessment, during the peritoneal catheter placement, for the detection and monitoring of infection, as well as for the evaluation of the catheter malfunction. Despite being not only a cost- and time-saving technique but also a bedside procedure, ultrasonography remains an underrated clinical tool in the field of peritoneal dialysis. This publication wants to explain and reinforce the clinical utility of US in PD and to expand the diagnostic equipment for the clinician.

Epidemiology, management, and prevention of exit site infections in peritoneal dialysis patients

Exit site infection (ESI) is a leading complication of peritoneal dialysis (PD), at an incidence of 0.6 episodes per year in the United States, and a major risk factor for catheter removal and peritonitis. An estimated 20% of all peritonitis cases are preceded by an ESI, with up to 50% of Staphylococcus aureus peritonitis associated with ESI. Gram-negative ESIs are less associated with succeeding peritonitis than their gram-positive counterparts, though when present, are associated with a lower peritonitis cure rate. The rate of catheter removal for refractory ESI is relatively highest in ESI due to mycobacteria (up to 40%), S. aureus (35%), Pseudomonas aeruginosa (28%), followed by Corynebacterium, Serratia, and fungi. In review of relevant literature, we found no prophylactic benefit of dressings over nondressings, specific antiseptics over normal saline, or topical honey over topical antibiotic prophylaxis, and thus recommend individualized exit site hygiene. We found topical gentamicin effective for prevention of most ESIs, including gram-negative ESIs, and thus recommend consideration of prophylactic topical gentamicin in areas of high gram-negative peritonitis incidence. With long-term use, observational studies detect up to 25% of gram-positive and 14% of gram-negative ESIs may be mupirocin and gentamicin resistant, respectively. We review empiric and targeted ESI management, including indications for ultrasound, anti-VMRSA, anti-Pseudomonal, and anti-mycobacterial antibiotic use, and catheter removal. We recommend further investigation into the earlier use of second-line treatment agents and the utility of treating post-infectious exit site colonization as avenues to decrease refractory and repeat ESI.

The impact of the superficial cuff position on the exit site and tunnel infections in CAPD patients

BACKGROUND

Peritoneal dialysis (PD) related infections continue to be a major cause of morbidity and mortality in patients on PD. In the last ten years, in order to reduce cuff and exit-site infections, in continuous ambulatory peritoneal dialysis (CAPD) patients, we have positioned the superficial cuff subcutaneously 4 cm instead of 2 cm internal to the exit-site.

METHODS

We analysed the infective episodes occurred in 123 CAPD patients (88 men and 35 women, mean age 62.4 ± 16.8) treated for 3337 months between 1st January 2011 and 31th December 2018 at Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico.

RESULTS

31 of the 123 patients (25.2%) developed 52 episodes of exit site infection, with an incidence of 1 episode every 64.1 patient-months. The cumulative probability of remaining infection free was 80.7% at 12 months and 61.8% at 36 months. Gram-positive organism accounted for 78.7% of exit site infections. Forty-one episodes (87%) were successfully treated with medical therapy. Peritonitis incidence was 1 episode every 51.7 and 1 episode every 49.2 patient-months, in patients with or without a history of exit site infection respectively. The overall incidence of tunnel infection was 1 episode every 278.1 patient-months.

CONCLUSIONS

Positioning the superficial cuff subcutaneously at least 4 cm internal to the exit-site might prevent the bacterial cuff colonization and reduce ESIs, tunnel infections and peritonitis.

Recurrent Infection and Catheter Loss in Patients on Continuous Ambulatory Peritoneal Dialysis

Objective

To elucidate the factors leading to catheter loss from recurrent infection in patients on continuous ambulatory peritoneal dialysis (CAPD).

Design

All catheters removed from patients were prospectively examined for infection.

Setting

CAPD unit in large tertiary-care general hospital.

Patients

Sixty-five consecutive patients undergoing catheter removal for whatever cause; 20 catheters rejected because of desiccation or contamination in transit.

Interventions

None.

Main Outcome Measures

Micro-organisms linked to catheter removal; their locations on removed catheters.

Results

Of 45 catheters removed between January 1994 and August 1995, 26 were infected: 13/26 infections were caused by Staphylococcus aureus and 7/26 by Pseudomonas aeruginosa. In only one case was S. epidermidis associated with catheter removal. The most striking finding was that the inner cuff harbored large numbers of the infecting organisms, even when antibiotics had eradicated them from the peritoneal cavity and exit site, where present, and the catheter lumen.

Conclusion

The importance of S. aureus and Ps. aeruginosa rather than S. epidermidis in catheter loss due to relapsing infection is confirmed. Persistence of the causative organisms in the inner cuff is a likely explanation for relapse after treatment, and might be due to the predominantly intraperitoneal administration of antibiotics. A clinical trial of the effect on catheter retention of empirical use of systemic or oral agents that give high tissue levels and are active against intracellular microorganisms, along with recommended intraperitoneal regimens, is indicated.

Peritoneal Dialysis Cuff-Shaving-A Salvage Therapy for Refractory Exit-Site Infections

Introduction:Cuff-shaving has been described as a salvage technique for refractory exit-site infections, with conflicting data regarding infection and catheter outcomes. We describe our experience with cuff-shaving as a rescue therapy for exit-site infections unresponsive to systemic therapy.Methods:We retrospectively reviewed patients who underwent cuff-shaving between January 2012 and June 2017. Refractory exit-site infection was defined as purulent discharge from the exit site with no clinical response after 3 weeks of systemic antibiotic treatment.Results:Fifty-three cuff-shavings were included, mean age was 53.4 ± 13.4 years, 26 patients were male. Median dialysis vintage was 29 months (interquartile range [IQR] 14.3 - 38), and 39 (73.6%) were on continuous ambulatory peritoneal dialysis (CAPD). The exit-site infection rate before cuff-shaving was 1.12 episodes per patient-year and the median time from infection to shaving was 52 days (IQR 35 - 76). The most frequent agents were Staphylococcus aureus (34%), Corynebacterium spp. (17%) and Pseudomonas aeruginosa (15%). Median follow-up was 9 months (IQR 1 - 18.5), during which time 35 catheters were removed, 5 due to non-infectious reasons. Using the Kaplan-Meier survival analysis, median catheter survival was 24 months (95% confidence interval [CI] 4.17 - 43.83). At 12 months, the probability of catheter survival was 54% and was not statistically different between gram-positive and gram-negative agents, although it was significantly shorter for fungal agents.Conclusion:Cuff-shaving is a feasible rescue therapy to treat refractory exit-site infections. In our experience, it allowed resolution of infections in a significant proportion of cases, except for fungal agents, and therefore extended catheter survival time, besides being associated with a small rate of complications.

Imaging Work-Up for Peritoneal Access Care and Peritoneal Dialysis Complications

Peritoneal dialysis (PD) represents a treatment opportunity for patients with end-stage renal failure, but it has particular complications that sometimes force cessation of this procedure (1–9). These complications are due to the presence of the peritoneal catheter and of dialysis solution within the peritoneal cavity. Infections are the most common complications of PD, followed by mechanical complications.

Diagnostic imaging of the complications of PD is important because such an evaluation can aid in the diagnosis and in the decision making process about the treatment. In this review we present the main radiologic investigations employed: plain radiograph, US, peritoneography, computed tomography peritoneography, magnetic resonance peritoneography, peritoneal scintigraphy.

To diagnose catheter-related problems plain radiograph, ultrasonography and peritoneography can be useful. US is useful in diagnosing and following-up exit-site and tunnel infections. Peritoneography and C T-peritoneography, alone or in combination, can be recommended as gold standard investigation to assess mechanical peritoneal dialysis complications, such as catheter malfunction, leaks, hernias and sclerosing peritonitis. Newer methods, such as MR peritoneography or scintigraphy could be useful in selected patients, on center-based experience. An appropriate use of radiology may significantly improve technique survival, morbidity and mortality of patients treated with PD.

Radiological diagnosis of dialysis-associated complications

In daily clinical practice, the radiologist in the context of diagnosis often faces dialysis-associated complications. The complications are numerous and range from infections, catheter dysfunctions, haematomas, cardiovascular diseases, digital ischaemia, and pseudoaneurysms to shunt stenosis. In this pictorial essay, we take a close look at the imaging diagnostics of the most common complications in dialysis patients. Teaching Points • The occurrence of venous stenosis in haemodialysis patients is up to 41 %. • Catheters usually have a fibrin sheath that can be rinsed but not aspirated. • The steal phenomenon occurs in 75-90 % of patients with a shunt system. • Arterial pseudoaneurysms can cause a number of complications.

Peritoneal dialysis associated infections: An update on diagnosis and management

Peritoneal dialysis (PD) is associated with a high risk of infection of the peritoneum, subcutaneous tunnel and catheter exit site. Although quality standards demand an infection rate < 0.67 episodes/patient/year on dialysis, the reported overall rate of PD associated infection is 0.24-1.66 episodes/patient/year. It is estimated that for every 0.5-per-year increase in peritonitis rate, the risk of death increases by 4% and 18% of the episodes resulted in removal of the PD catheter and 3.5% resulted in death. Improved diagnosis, increased awareness of causative agents in addition to other measures will facilitate prompt management of PD associated infection and salvage of PD modality. The aims of this review are to determine the magnitude of the infection problem, identify possible risk factors and provide an update on the diagnosis and management of PD associated infection. Gram-positive cocci such as Staphylococcus epidermidis, other coagulase negative staphylococcoci, and Staphylococcus aureus (S. aureus) are the most frequent aetiological agents of PD-associated peritonitis worldwide. Empiric antibiotic therapy must cover both gram-positive and gram-negative organisms. However, use of systemic vancomycin and ciprofloxacin administration for example, is a simple and efficient first-line protocol antibiotic therapy for PD peritonitis - success rate of 77%. However, for fungal PD peritonitis, it is now standard practice to remove PD catheters in addition to antifungal treatment for a minimum of 3 wk and subsequent transfer to hemodialysis. To prevent PD associated infections, prophylactic antibiotic administration before catheter placement, adequate patient training, exit-site care, and treatment for S. aureus nasal carriage should be employed. Mupirocin treatment can reduce the risk of exit site infection by 46% but it cannot decrease the risk of peritonitis due to all organisms.

Ultrasound evaluation of peritoneal catheter tunnel in catheter related infections in CAPD

In cases of peritonitis and exit site infections it is important to determine the extent of involvement of the subcutaneous catheter tract. The assessment of such involvement by physical examination alone appears to be inadequate and insensitive. We examined the usefulness of ultrasound (US) examination of the catheter tract in delineating catheter related infections, and their relationship to each other and to peritonitis. Patients were examined during clinically defined states of exit-site infection (ESI), clinically defined tunnel infection (TI), peritonitis and in the normal condition. US examinations of the catheter tunnel were performed in 44 CAPD patients. A total of 47 US examinations (examination was repeated in three patients) were performed, divided among 13 episodes of peritonitis, four ESI, and 30 controls. In 12 of 47 US examinations, US-defined TI was demonstrated as a sonolucent pericatheteric fluid collection. These 12 positive US were distributed among seven patients with peritonitis, three with exit-site infections and two control patients. We conclude that peritonitis and ESIs are frequently accompanied by involvement of the catheter tract. It seems that both the internal and external cuffs do not constitute an effective barrier against the spread of infection.

Salvage of problematic peritoneal dialysis catheters

Peritoneal dialysis (PD) is a markedly underutilized modality for permanent renal replacement therapy in the United States owing to a low rate of patient referral and high rate of patient dropout or transfer to hemodialysis. One cause for patient loss from PD is problematic PD catheters that often are removed rather than being subjected to simple surgical salvage procedures. We report three patients with problematic catheters and our approach to their management. The first patient developed erosion of the skin overlying the portion of the catheter between the deep and superficial cuffs after 6 months of PD. The second patient developed extrusion of the superficial cuff after 4 years of PD. The third patient demonstrated a localized abscess at the incision site for catheter insertion after 3 years of PD. Other than a mild superficial exit site infection and localized abscess in the second and third patient, respectively, there were no associated infections of the catheter tunnel and cuff or of the peritoneal cavity as determined by either clinical examination, ultrasound evidence of fluid collection, or cultures and white blood cell counts. All three cases were managed successfully by interventional nephrology on an outpatient basis and under local anesthesia without either catheter removal or placement of a new PD catheter. It was possible to continue uninterrupted PD in the first and third patients, while the second patient had temporary hemodialysis to allow for complete healing of the surgical wound. We conclude that in selected cases simple interventions can salvage problematic PD catheters and maintain patients on PD.

Peritoneal Catheters and Related Infections

Catheter related infectious complications (exit-site infections, tunnel infections, and peritonitis) remain the major reasons for technique failure during the three decades since, continuous ambulatory peritoneal dialysis (CAPD) treatment has been first established. Despite improvements in catheter's survival rates, catheter related complications result in an increase in the cumulative patients' morbidity and often leading to the catheter removal. The ideal catheter provides reliable and rapid dialysate flow rates without leaks or infections. Among several types, the double-cuff straight Tenckhoff catheter, developed in 1968, is still the most widely used, although its use is decreasing in favour of swanneck catheters. Although there are only few well-designed trials comparing catheters and catheters related infectious complications, controlling for all other important variables, no difference in these complications among the main types of catheters was seen. The single cuff catheters have been associated with a shorter survival rate and time to the first peritonitis episode than the double-cuff catheters. Also exit-site infections were found to be more frequent and significantly more resistant to treatment with single-cuff compared to double-cuff ones. Finally, better results have been reported with the latest developed presternal peritoneal dialysis catheter both regarding survival rates and exit-site infection and peritonitis rates. Recently a renewed interest in continuous flow peritoneal dialysis stimulated inventions of imaginative, double-lumen catheters since a suitable peritoneal access is a sine qua non condition for the development of this new technique of peritoneal dialysis.

Ultrasonography in the management of exit site infections in peritoneal dialysis patients

AIM

To assess the efficacy of using ultrasonography (USG) in monitoring the progress of exit site infection (ESI) in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

METHODS

Twenty-two cases of newly diagnosed ESI and 20 cases with normal exit sites as controls were assessed by using USG. The exit sites were reassessed by using USG after finishing a course of antibiotic therapy, and the sonographic findings were correlated with the clinical outcome.

RESULTS

Out of the 22 cases of ESI, 21 cases had definite sonolucent zones around the external cuffs, while one case had normal sonographic findings. Of the 20 control cases of normal exit sites, 16 had normal sonographic findings, and four had sonolucent zones around the external cuffs. Exit site infections correlated with positive sonographic findings as compared to normal exits (P <0.0001). The 21 cases of ultrasonic-positive ESI were re-examined after antibiotic therapy, and 10 of these had a post-treatment sonolucent rim around the distal cuff < or =1 mm thick, while 11 cases were persistently > mm thick. The former group was shown to have a more favourable outcome (P=0.013). And despite variable USG findings, all eight patients with Pseudomonas aeruginosa-related ESI had an unfavourable clinical outcome.

CONCLUSION

Ultrasonography of the exit sites in CAPD patients is a useful adjunctive tool in the management of ESI. A sonolucent zone around the external cuff >1 mm thick following a course of antibiotic treatment and the involvement of the proximal cuff are associated with poor clinical outcome. In ESI caused by Pseudomonas aeruginosa, the clinical outcome was uniformly poor irrespective of the sonographic findings.

Tenckhoff catheters post-renal transplantation: the 'pull' technique?

BACKGROUND

Tenckhoff catheters are used widely for the provision of continuous ambulatory peritoneal dialysis. Traditionally these catheters are removed surgically under anaesthesia. We set out to introduce and monitor prospectively a technique for removal of the Tenckhoff catheter by a 'pull' technique. The intention was to avoid the discomfort, risk and cost of traditional surgery.

METHODS

Over a 1-year period all renal transplant patients having their Tenckhoff catheter removed by this technique were monitored prospectively. All patients were followed for a minimum 2-year period after removal. In the pull technique steady non-jerky traction is applied to the catheter. Complications such as catheter breakage and cuff related sepsis were recorded.

RESULTS

Sepsis related to a retained cuff occurred in only one patient early in the series. There were no other complications. The procedure was well tolerated. Use of local anaesthesia used initially, was largely phased out over the course of study and the procedure moved from the theatre to the ward.

CONCLUSIONS

The pull technique is safe and well tolerated. The technique has significant advantages in selected patients without a history of recent peritonitis or exit site infection, in reducing risk to the patients, the pain of abdominal wall surgery and reduced usage of costly theatre time and in-patient beds.

Peritoneal dialysis. Prevention and control of infection

In spite of the reduction in peritonitis and catheter-related infection rates in patients undergoing peritoneal dialysis, these infections remain major sources of morbidity and transfer to haemodialysis. Touch contamination at the time of doing the exchanges is still a major cause of peritonitis and leads to Gram-positive organisms (coagulation-negative staphylococcus) being the most common pathogens. Newer exchange techniques have reduced this incidence but the more serious pathogens (Staphylococcal aureus, pseudomonas and fungi) remain a major problem. Treatment has to be immediate, and hence empirical, giving adequate cover for both Gram-positive and Gram-negative organisms. The use of vancomycin as an initial antibacterial has been discontinued because of the problem of vancomycin-resistant enterococcus. Recent guidelines advocate the use of a first generation cephalosporin combined with ceftazidime (if the urine output is >100 ml/day) or an aminoglycoside in anuric patients. Subsequent therapy changes are made upon bacterial isolation and sensitivities. Vancomycin is reserved for methicillin-resistant staphylococcus. Peritoneal catheter-related infections (exit site and tunnel) are predominantly caused by S. aureus and pseudomonal organisms and can be difficult to eradicate. Tunnel infections invariably involve the catheter dacron cuffs and therefore are more likely to lead to peritonitis; in this situation catheter removal is the treatment of choice. Treatment of exit-site infections is with oral antibacterials (penicillinase-resistant penicillins, cefalexin). Vancomycin is avoided if possible. The identification that nasal carriage of S. aureus predisposes to exit-site and tunnel infections has led to prophylactic regimens to combat this problem. Mupirocin applied at the exit site leads to a reduction in catheter-related infections and peritonitis.

Peritoneal infections

Peritoneal dialysis related infections include infection of the catheter exit site, subcutaneous pathway, or effluent. Exit-site infections, predominately owing to Staphylococcus aureus, are defined as purulent drainage at the exit site, although erythema may be a less serious type of exit-site infection. Tunnel infections are underdiagnosed clinically, and sonography of the tunnel is useful to delineate the extent of the infection and to evaluate response to antibiotic therapy. S aureus infections occur more frequently in S aureus carriers and immunosuppressed patients and can be reduced by mupirocin prophylaxis either intranasally or at the exit site. Patients with peritonitis present with cloudy effluent and usually pain, although 6% of patients may initially have pain without cloudy effluent. A white blood cell count of 100 or greater per microL, 50% of which are polymorphonuclear cells, has long been the hallmark of peritonitis. Empiric therapy is controversial, with some recommending cefazolin and others vancomycin (with cefatazidime for Gram-negative coverage). The choice should depend on the center's antibiotic sensitivity profile; those centers with a high rate of Enterococcus- or methicillin resistant organisms should use vancomcycin. Peritonitis episodes occurring in association with a tunnel infection with the same organism seldom resolve with antibiotics and require catheter removal. Other indications for catheter removal are refractory peritonitis, relapsing peritonitis, tunnel infection with inner-cuff involvement that does not respond to antibiotic therapy (based on ultrasound criteria), fungal peritonitis, and enteric peritonitis owing to intra abdominal pathology. Centers can reduce dialysis related infections to very low levels by proper catheter selection and insertion, careful selection and training of patients, avoidance of spiking techniques, and use of antibiotic prophylaxis against S. aureus. Further research is required to identify methods to reduce the risk of enteric peritonitis.

Ultrasonography of the catheter tunnel in peritoneal dialysis patients: what are the indications?

The importance of sonography for the early detection and follow-up of tunnel infections in peritoneal dialysis patients is well documented, whereas other indications are less clear. We investigated indications and outcome of 738 ultrasound examinations of the peritoneal dialysis catheter tunnel. Indications for tunnel sonography included routine screening (27%), exit-site infection without peritonitis (24.1%), follow-up of tunnel infection (29.5%), clarification of questionable results (7.5%), pain in the course of the catheter tunnel (1.8%), peritonitis without (5.3%) and with (2.0%) exit-site infection, search for foci (2.2%), and recurrent peritonitis (0.7%). No positive sonographic results were obtained during routine screening or in patients with fever or elevated C-reactive protein levels showing no clinical signs of exit-site infection. Sonographic examinations were positive in 1 of 13 patients with pain in the course of the catheter tunnel, in 1 of 39 cases of peritonitis not associated with exit-site infection, in 12 of 15 patients with peritonitis and simultaneous exit-site infection, and in 2 of 5 patients with recurrent peritonitis. Questionable results were detected in 15 of 178 patients with exit-site infection, in 15 of 199 routine examinations, in 2 of 16 examinations of patients with elevated C-reactive protein levels or fever, and in 2 of 15 cases of peritonitis and simultaneous exit-site infection. All but two of these questionable results had to be rated as negative during further follow-up. We conclude that tunnel sonography is indicated in patients with exit-site infection (including cases with simultaneous peritonitis), for follow-up of tunnel infections, and for estimating the prognosis of these infections. Furthermore, tunnel sonography should be performed in patients with recurrent peritonitis. Tunnel sonography is not indicated for routine screening, search for foci, in cases of peritonitis without exit-site infection, or in patients with pain in the course of the catheter tunnel showing no other clinical signs of exit-site infection.