Trapped Below: Abdominal Pseudocysts Associated With Ventriculoperitoneal Shunts in Coccidioidal Meningitis

Abstract

Ventriculoperitoneal (VP) shunts are the mainstay for cerebrospinal fluid diversion in patients with refractory coccidioidal meningitis (CM)-associated hydrocephalus. Abdominal pseudocysts (APCs), an uncommon but known complication of distal shunt catheters, have not been well described in CM. We conducted a retrospective study of 124 patients with CM who underwent VP shunt placement between 2010 and 2024. APCs occurred in 21 patients (17%), with most presenting with symptoms of shunt malfunction rather than abdominal complaints. This incidence is notably higher than previously reported in patients with hydrocephalus due to other etiologies. Evidence of active Coccidioides infection was present in 71% of patients. Imaging typically revealed fluid collections at the distal catheter tip, and most patients underwent surgical intervention targeting the distal shunt. Despite intervention, recurrent shunt failures occurred in a substantial proportion. These findings add to the limited literature on APCs in CM and may inform future research into their presentation, contributing factors, and management.

Coccidioidal meningitis (CM), a devastating complication of disseminated coccidioidomycosis, is a chronic infection with protean manifestations [1]. One of its most common and feared complications is hydrocephalus, the accumulation of cerebrospinal fluid (CSF) within the cerebral ventricles, which can lead to a range of symptoms and may be fatal if not managed promptly [2]. While obstructive hydrocephalus results from a physical blockage in CSF flow, communicating hydrocephalus arises from impaired absorption [3]. In coccidioidal infection, basilar meningitis develops, and the resulting severe inflammation produces proteinaceous debris and arachnoid fibrosis, ultimately impairing CSF absorption and leading to communicating hydrocephalus [4].

Management often requires the placement of CSF-diverting shunts, with ventriculoperitoneal (VP) shunts being the most commonly used method [5]. However, despite antifungal therapy and CSF diversion, shunt-related complications are not uncommon in patients with CM [6]. The most frequent issues are shunt malfunction and obstruction. Distal shunt complications include migration, CSF ascites, and intra-abdominal pseudocysts (APCs) [7]. APCs form when CSF resorption at the distal site is impaired, resulting in a localized collection of CSF encapsulated by a non-epithelial serosal lining [8]. These cysts can cause symptoms and further compromise shunt function.

While APCs are well-documented in pediatric patients with congenital hydrocephalus, there is a lack of literature describing this complication in patients with CM [9–11]. This study aims to characterize the clinical presentation, underlying causes, imaging findings, and management strategies of APCs in patients with CM. Although APC is an uncommon complication, physicians managing patients with chronic infections requiring VP shunts should be familiar with its presentation and appropriate management.

METHODS

A retrospective chart review was conducted of patients diagnosed with CM at Community Regional Medical Center (CRMC) between 2010 and 2024, using ICD-9 and ICD-10 diagnostic codes. CRMC is a high-volume, 750-bed academic medical center affiliated with the University of California, San Francisco Fresno program. Located in California's San Joaquin Valley, a region highly endemic for coccidioidomycosis, it serves as a major referral center for multiple surrounding counties and cities.

Patients were included if they had a diagnosis of CM, had VP shunt placement, and were subsequently diagnosed with APCs based on radiologic or intraoperative findings. Patients with incomplete medical records or unclear diagnoses were excluded from the analysis.

Data collected included patient demographics, underlying medical conditions, clinical presentation, VP shunt characteristics, imaging findings, and management strategies.

DEFINITIONS

APCs were defined as localized, CSF-filled collections at the distal tip of the VP shunt catheter, typically identified by computed tomography (CT) or confirmed intra-operatively.

Active coccidioidal infection was defined as meeting at least one of the following criteria:

1. Culture of APC fluid, CSF, or shunt tubing positive for Coccidioides species.

2. Positive Coccidioides PCR or antigen from APC fluid, CSF, or shunt tubing.

3. Increasing serum or CSF complement fixation titers.

Serum and CSF complement fixation and immunodiffusion tests were performed locally at the CRMC laboratory and referred to the University of California, Davis laboratory for confirmation. The Coccidioides immitis real-time PCR assay was developed in our center's laboratory using the BD Max system [12]. The study was reviewed and approved by the Institutional Review Board at CRMC.

RESULTS

We identified 124 patients with CM who required VP shunt placement for the management of hydrocephalus during the study period. Of these, 21 patients (17%) developed APCs and were included in the final analysis (Table 1). The median age at CM diagnosis in patients with APC was 33 years (interquartile range [IQR]: 26.5–45.3). Most patients were White (76%), and 62% identified as not Hispanic or Latino. Underlying immunocompromising conditions were infrequent, with diabetes and HIV each present in 3% of patients, cancer in 2%, and other immunocompromising conditions (pregnancy and cirrhosis) in 5%.

Table 1.

Characteristics of CM Patients With APC Complicating VPS (n = 21)

Patient	Agea/Sex/Race/Ethnicity	Comorbidities	Duration of CM Before APC (y)	Duration of VPS Before APC (y)	Prior Shunt Revision Surgeries (n)	Symptoms	Evidence of Active Coccidioidal Infection	Prior Anti-fungal Therapy	APC Management	Status of Life
1	25/Male/White/Hispanic	Cancer	2	2	None	Abdominal	Not available	Fluconazole	Lap drainage, distal revision	Alive
2	43/Male/White/Not Hispanic	None	9	2	1	Abdominal	Yes	Fluconazole → voriconazole → posaconazole	Entire shunt replacement	Alive
3	34/Male/White/Hispanic	None	5	5	None	CNS	Yes	Fluconazole	Entire shunt replacement	Alive
4	32/Male/Black/Not Hispanic	None	7	3	3	CNS	Yes	Fluconazole → voriconazole → posaconazole	Lap drainage, externalization of distal tube	Expired
5	24/Male/Asian/Not Hispanic	None	5	1	None	CNS	Yes	Fluconazole	Lap drainage and distal tube re-insertion	Alive
6	27/Male/White/Not Hispanic	None	11	7	3	CNS	Yes	Fluconazole	Lap drainage and distal tube re-insertion	Alive
7	21/Female/Black/Not Hispanic	Diabetes mellitus	5	2	2	CNS	Not available	Fluconazole	Lap drainage and distal tube re-insertion	Alive
8	34/Male/White/Not Hispanic	None	21	4	None	CNS and abdominal	Yes	Fluconazole	Lap drainage and distal tube re-insertion	Alive
9	59/Female/White/Not Hispanic	None	3	2	1	CNS	Yes	Fluconazole	No drainage	Expired
10	50/Male/White/Not Hispanic	None	1	1	None	CNS	Not available	Fluconazole	Lap drainage and distal tube re-insertion	Expired
11	15/Male/White Hispanic	None	18	2	1	CNS	Not available	Fluconazole	Lap drainage, distal revision	Alive
12	31/Female/White/Hispanic	None	6	4	3	CNS	Not available	Fluconazole	Entire shunt replacement	Expired
13	20/Female/White/Not Hispanic	Pregnancy at diagnosis	8	6	2	Abdominal	Not available	Fluconazole	Lap drainage, distal revision	Alive
14	44/Male/White/Hispanic	HIV†	2	2	None	CNS	Yes	Fluconazole	Entire shunt replacement	Alive
15	44/Female/Black/Not Hispanic	None	1	1	1	CNS	Yes	Intra-thecal amphotericin B	No drainage	Alive
16	49/Male/White/Hispanic	Alcoholic cirrhosis	1	1	1	CNS	Yes	Fluconazole	Lap drainage, externalization of distal tube	Expired
17	29/Male/White/Hispanic	None	2	0.5	None	Abdominal	No	Fluconazole	Per cutaneous drainage	Alive
18	52/Male/White/Hispanic	Asthma, Stroke	3	3	None	CNS and abdominal	Yes	Fluconazole	Lap drainage, distal revision	Alive
19	19/Male/White/Hispanic	None	6	3	None	CNS and abdominal	Yes	Fluconazole	Lap drainage, distal revision	Alive
20	40/Male/White/Not Hispanic	HIV	5	5	1	CNS	Yes	Fluconazole	Lap drainage, distal revision	Expired
21	38/Male/Black/Not Hispanic	Diabetes mellitus	11	6	3	CNS	Yes	Fluconazole → voriconazole	Lap drainage, distal revision	Expired

APC, abdominal pseudocyst; CM, coccidioidal meningitis; CNS, central nervous system; LAP, laparoscopic; VPS, ventriculo-peritoneal shunt.

^aAge at the time of CM diagnosis.

CLINICAL COURSE OF COCCIDIOIDAL MENINGITIS

The median duration of CM prior to the development of APC was 5 years (IQR: 2–8), and the median interval from VP shunt placement to APC onset was 2 years (IQR: 2–4). Prior shunt revision was documented in 57% of patients, half of whom had undergone more than one revision. In terms of antifungal management, 33% (7/21) of patients had documented non-adherence, 14% (3/21) experienced intolerance, and 19% (4/21) were treated with multiple azole agents due to therapeutic challenges. The underlying reasons for non-adherence (eg, cost, intolerance, or substance use) were not consistently documented. Given the sample size, no meaningful statistical correlation with outcomes could be determined. Only one patient (patient 15) received intrathecal amphotericin B.

All patients had VP shunts equipped with programmable valves, which allow noninvasive external adjustment of opening pressure using a magnetic device. Valve settings in this cohort ranged from 0.5 to 2.0. The most commonly used valve model was Medtronic Strata (85%), followed by Codman Certas (10%). Programmable valves are frequently selected in patients with chronic hydrocephalus due to their ability to accommodate evolving clinical needs without requiring surgical revision. In all but two patients, shunts were placed in the lateral ventricles. One patient had shunts in the lateral foramen of Monro and fourth ventricles, while another had placement at the third ventricle.

CLINICAL PRESENTATION AND LABORATORY RESULTS

The median symptom duration before APC diagnosis was 4 days; all patients were symptomatic. At presentation:

• 14% (3/21) had isolated abdominal symptoms,

• 67% (14/21) had only central nervous system (CNS) symptoms, and

• 19% (4/21) had both.

Abdominal complaints included generalized or localized pain, bloating, and vomiting. CNS symptoms most commonly involved altered mentation, along with headache, dizziness, ataxia, lethargy, tremors, and nausea.

Active coccidioidal infection was confirmed in 13 patients via culture of C. immitis species or molecular testing of APC fluid, shunt tubing, or CSF. In total, 71% met criteria for active infection within the prior 3 months. In three patients (cases 2, 3, and 21), fungal growth was observed directly on the distal catheter tip. APC wall biopsies were performed in five patients, with three showing granulomatous inflammation and fungal elements. In one patient (case 20), hyphal forms were identified in the APC wall biopsy. Peritoneal fluid analysis in this patient showed a white blood cell (WBC) count of 1107 (80% neutrophils), and the CSF WBC count was 13 cells/µL. Methicillin-sensitive Staphylococcus aureus co-infection was identified in two patients.

Serum complement fixation titers within the preceding 3 months were available for 10 patients, ranging from 1:16 to 1:128 (median, 1:32). CSF complement fixation titers were available for six patients, ranging from 1:2 to 1:64 (median, 1:8). All patients with available titers met criteria for active infection, due to either elevated levels or rising titers compared with prior values. No patients demonstrated findings consistent with resolved or quiescent infection.

IMAGING FINDINGS

Abdominal imaging (CT) demonstrated fluid collections or cysts at the distal catheter tip in 81% of cases. In the remaining patients (19%), collections were either identified intraoperatively or not visualized on imaging (Figure 1A–D). The size of abdominal fluid collections ranged from 2.9 to 21.2 cm in the greatest dimension.

Figure 1.

A–D, Abdominal CT demonstrating abdominal pseudocysts at the distal tip of VP shunts in patients with CM. A, Patient 2: 52-year-old male with a 9-year history of CM and prior shunt revision presented with one day of acute abdominal pain. CT revealed a large pseudocyst measuring 21.2 × 7.6 × 11.2 cm. Shunt cultures grew C. immitis and MSSA. B, Patient 4: 39-y-old male with a 7-y history of CM and three prior shunt revisions presented with five days of altered mentation, confusion, ataxia, and dizziness. Abdominal CT revealed an 11.8 × 4.7 × 7.0 cm pseudocyst. Brain MRI showed worsening hydrocephalus. Shunt cultures grew C. immitis. C, Patient 18: 55-y-old male with a 3-y history of CM presented with three days of right-sided abdominal pain, headache, and altered mentation. Imaging revealed a 13.0 × 11.5 × 5.4 cm pseudocyst and worsening hydrocephalus. CSF cultures were positive for C. immitis. D, Patient 16: 50-y-old male with a 1-y history of CM and one prior shunt revision presented with three days of headache and lethargy, without abdominal symptoms. Imaging revealed a 16.5-cm pseudocyst and worsening hydrocephalus. Pseudocyst fluid was positive for Coccidioides by PCR. Serum complement fixation titer was 1:128. CM, coccidioidal meningitis; CSF, cerebrospinal fluid; CT, computed tomography; MSSA, methicillin-sensitive Staphylococcus aureus; VP, ventriculoperitoneal.

Concomitant head imaging (CT or magnetic resonance imaging [MRI]) revealed worsening hydrocephalus, often with trans ependymal flow in 52% of patients. In three patients (14%), MRI findings were concerning for ventriculitis at the time of shunt replacement.

MANAGEMENT AND OUTCOMES

All but two patients underwent procedural intervention (Figure 2). Antibiotics were given for bacterial co-infection in two cases, and antifungal therapy was modified in three.

Figure 2.

Management strategies for abdominal pseudocysts in patients with VP shunts (n = 21). Nineteen patients underwent procedural intervention. Fourteen were managed with distal shunt-directed approaches: laparoscopic drainage with distal revision (n = 6), distal reinsertion in the same setting (n = 4), and externalization with delayed replacement (n = 4). Four patients required a complete shunt system revision. One patient underwent percutaneous pseudocyst drainage alone. Two patients did not undergo any procedure. VP, ventriculoperitoneal.

Among the 17 patients who initially retained their shunt, 8 patients (47%) experienced recurrent shunt failure requiring complete system revision or removal within 3 months. Of the seven who avoided full revision at 3 months, three (43%) later required revision within 12 months. Recurrence of APC was documented in 4 patients. Overall mortality was 28.6% (6 of 21 patients). Patients who died during follow-up are indicated in Table 1.

DISCUSSION

Basilar meningitis due to CM triggers an intense host inflammatory response, leading to dense arachnoid fibrotic thickening and impaired CSF resorption at the arachnoid villi and basilar cisterns, resulting in communicating hydrocephalus [4]. Over 50% of patients with CM-related hydrocephalus need the placement of CSF-diverting shunts [13]. Cerebral shunts are life-saving devices that divert excess CSF, preventing elevated intracranial pressure, cerebral edema, herniation, and death. A standard shunt system comprises a ventricular catheter connected to a valve and a distal catheter [14]. The distal catheter may terminate in the peritoneal cavity, right atrium, or pleural space, corresponding to VP, ventriculoatrial, and ventriculopleural shunts, respectively. The peritoneal cavity is favored due to its absorptive capacity and low complication rates; therefore, VP shunts remain the primary modality for CSF diversion in patients with CM-associated hydrocephalus [15, 16].

Programmable shunt valves offer an important advantage in the management of patients with chronic, infection-associated hydrocephalus. Unlike fixed-pressure valves, programmable systems allow clinicians to adjust the opening pressure externally using a magnetic tool, enabling tailored CSF drainage without the need for surgical intervention [17]. This flexibility is particularly beneficial in patients with CM, who often have prolonged shunt dependence and evolving intracranial dynamics due to persistent inflammation, arachnoid scarring, or changes in CSF production and resorption. By permitting noninvasive adjustments in response to clinical symptoms or imaging findings, programmable valves reduce the need for repeat surgeries solely for pressure modification and may contribute to improved long-term shunt function in this population.

Although VP shunts can be lifesaving, patients with CM who require these devices frequently experience complications and shunt malfunctions [5]. Hardesty et al [6] reported a shunt failure rate of 66% in this population. In another study evaluating shunt outcomes in CM, mechanical obstruction accounted for 81% of shunt failures, attributed to proteinaceous fungal debris and biofilm formation within catheters and valve chambers. Complications related to VP shunts may be related to obstruction, mechanical kinking, loculations, infections, over-drainage, slit ventricle syndrome and distal shunt problems [7, 18].

Among distal shunt complications, APCs represent a particularly challenging and understudied problem. These loculated CSF collections at the distal catheter tip lack a true epithelial lining (hence “pseudo” cysts) and are instead surrounded by reactive fibrous or mesothelial tissue (Figure 3) [19, 20]. Although APCs have been described in pediatric hydrocephalus and noninfectious etiologies, their occurrence in CM-related shunting has received little focused attention. In a retrospective case–control study by Cummins et al [21], shunt outcomes were compared between patients with non-bacterial infection (NBI)-associated hydrocephalus and those with typical causes such as malignancy, congenital abnormalities, normal pressure hydrocephalus (NPH), and post-traumatic injury. Shunt failure was significantly more common in the NBI group, which included 93 patients who underwent shunt placement, 80 of whom (86.0%) had hydrocephalus due to coccidioidomycosis. APCs were identified as a more frequent cause of shunt malfunction in the NBI group compared with those with typical hydrocephalus (30.0% vs 2.6%; P < 1E−5 which is ∼ P < .001, as reported by Cummins et al), despite similar rates of bacterial infection, proximal and distal tubing obstruction, and valve dysfunction. Notably, 17 of the 18 pseudocyst cases occurred in patients with CM. This remains the only published study to date that describes APCs in the context of CM. Although the study noted a higher frequency of APCs in patients with CM compared with other causes of nonbacterial meningitis, it did not characterize their clinical presentation, microbiologic findings, or outcomes. In this context, we present a detailed analysis of 21 patients with CM who developed APCs after VP shunt placement.

Figure 3.

Illustration of a VP shunt complicated by an intra-abdominal pseudocyst at the distal catheter tip. VP, ventriculoperitoneal.

The incidence of APC in our CM cohort was 17%, substantially higher than the previously reported rates of 0.5%–7% in patients with hydrocephalus due to trauma, malignancy, NPH, or congenital causes [10, 11, 16, 19]. The precise mechanisms underlying APC formation remain unclear. Although chronic inflammation is widely regarded as the primary driver, other contributing factors such as prior abdominal adhesions and elevated CSF protein levels have also been proposed [22, 23]. In our cohort, 71% of patients had evidence of active coccidioidal infection at the time of APC diagnosis, raising concern that chronic inflammation secondary to ongoing fungal infection plays a significant role in pseudocyst development. The median duration of CM prior to APC onset was 5 years, underscoring the chronic nature of the disease and prolonged dependence on shunt hardware. Additionally, 57% of patients had a history of shunt revision, with half of these undergoing multiple revisions, suggesting that adhesions from prior surgeries may also have contributed to pseudocyst formation. While several clinical factors were observed among patients with APCs, the small sample size and absence of controls limited our ability to determine statistically significant associations.

Although APC formation is presumed to be a gradual process driven by chronic inflammation, most patients in our cohort presented with acute or subacute CNS or abdominal symptoms. This may reflect a threshold effect, where symptoms become clinically apparent only after sufficient shunt dysfunction or cyst expansion occurs. Additionally, many patients with longstanding CM experience baseline neurologic symptoms, which may delay recognition of new or worsening clinical signs.

While previous reports have suggested that patients with APCs often present with abdominal symptoms, 86% of our patients exhibited signs of shunt malfunction, such as altered mentation, headaches, ataxia, and vomiting as their primary presentation [19, 23]. Only 14% presented with isolated abdominal symptoms, suggesting that APC formation may be a more indolent process, with patients frequently presenting only after shunt dysfunction has already occurred. Given that abdominal symptoms were uncommon in our cohort, the potential value of routine abdominal imaging, such as ultrasound or CT, for earlier detection of APCs and prevention of shunt malfunction warrants further study.

Management strategies varied across the cohort. Most patients underwent surgical interventions targeting the distal portion of the shunt system, including laparoscopic drainage with shunt reinsertion, distal catheter revision, or externalization. Complete shunt system replacement was required in only four patients. Despite these interventions, 47% experienced recurrent shunt failure within 3 months, with additional failures documented by 12 months. APC recurrence was noted in four patients. Although APCs did not recur in most cases following drainage and distal shunt revision, shunt malfunction often persisted, suggesting that the underlying pathophysiologic process for APC development remained unaddressed. This raises the possibility that APCs may represent a marker, rather than the root cause of ongoing shunt dysfunction. Persistent inflammatory debris, possibly fungal in origin, or impaired CSF resorption may continue to compromise shunt function even after the pseudocyst is treated.

Notably, antifungal therapy was not escalated in most cases following APC diagnosis, despite microbiologic or serologic evidence of persistent Coccidioides activity in several patients. Although a causal relationship between antifungal failure and pseudocyst formation has not been established, these findings raise concern about the adequacy of fungal control in patients with chronic shunt dependence. Whether biofilm formation within shunt hardware contributes to persistent infection, and whether antifungal penetration into the shunt and peritoneal compartments is sufficient, remains to be studied.

This study has several limitations. As a retrospective, single-center analysis, it is subject to incomplete documentation, variability in diagnostic evaluations, and non-standardized follow-up. Microbiologic and histopathologic data were inconsistently available, and operative details were not uniformly reported. Due to non-standardized documentation and fragmented follow-up in some cases, we were unable to determine whether delays in re-shunting contributed to outcomes. The observational nature of the study also precludes conclusions about causality between infection, mechanical factors, and pseudocyst formation. Nevertheless, this study adds to the limited body of literature on APCs in CM and may inform future research into their pathogenesis and management.

In conclusion, APCs occurred in 17% of patients with CM-associated hydrocephalus who required VP shunt placement, and most presented with symptoms of shunt malfunction rather than abdominal complaints. Many had evidence of active Coccidioides infection at the time of diagnosis, and a substantial proportion experienced subsequent shunt failure, underscoring the need for further investigation into the pathogenesis and long-term management of this complication.