Primary tuberculous psoas abscess as a postpartum complication: Case report and literature review.

BACKGROUND: Primary psoas abscess is an unusual clinical entity rarely encountered in the postpartum period. Only seven cases have been reported to date. Here, we present a woman with a primary psoas abscess caused by Mycobacterium tuberculosis and occurred 2 months following a normal vaginal birth. We highlight the difficulties in the management of this uncommon condition in light of the relevant literature. CASE DESCRIPTION: A 34-year-old woman who was previously healthy was presented at 2 months' postpartum with important right sciatica and low back pain without fever. Examination of the abdomen revealed tenderness in the right iliac fossa but obstetric/gynecologic and neurologic examinations were normal. The patient had an elevated C-reactive protein level and computed tomography (CT)-scan demonstrated a large psoas abscess on the right side without sacroiliac or spine abnormalities. Initial posterior lumbar percutaneous drainage was useful, but no pathogens were identified. The patient was discharged home with oral antibiotics therapy (amoxicillin/clavulanate and metronidazole). Four weeks later, the follow-up CT-scan showed a re-accumulation of the abscess cavity. Subsequently, the patient underwent a right anterolateral laparotomy with a retroperitoneal approach for abscess drainage. Again, no microorganisms were found. However, diagnosis of tuberculosis was established on histopathologic study. She was successfully treated with antituberculous drugs with a good outcome.
CONCLUSIONS: Most primary psoas abscesses present with a delay in diagnosis because of the rarity of this infectious disease, the lack of specific symptoms and signs, and its similarity to many differential diagnoses. When suspected, CT-scan and/or magnetic resonance imaging help in making an accurate diagnosis and facilitate percutaneous or open surgical drainage of the abscess. Correct and fast identification of the microorganisms in addition to appropriate usage of antibiotic regimen improves the outcome.

INTRODUCTION

Since the first description of psoas (or iliopsoas) muscle abscess by Herman Mynter in 1881,[18] this infection has been recognized as infrequent, insidious, misdiagnosed, and a potentially life-threatening condition.[820] Psoas abscess can be either primary or secondary, depending on the presence or absence of an underlying infectious disease. Staphylococcus aureus is the most frequently isolated pathogen.[920] Primary (isolated) tuberculous psoas abscess is currently uncommon and often associated with a concomitant spondylodiscitis (Pott's disease).[16] Primary psoas abscess (PPA) is a rare complication in general obstetrics and gynecology. In addition, the diagnosis may be a particular challenge because pain in the lower back and buttocks is common and often nonspecific during pregnancy and the postpartum period. To the best of our knowledge, only six cases of PPAs were reported during ongoing pregnancy,[26] two cases in the postabortal period,[1222] and seven cases in the postpartum period.[451319212429]

We present a woman who was found to have a primary tuberculous psoas abscess in the postpartum requiring two surgical drainages. We highlight the difficulties in the management of this uncommon condition in light of the relevant literature.

CASE REPORT

After a normal pregnancy and an uneventful vaginal birth of a healthy female infant, a 34-year-old biparous woman presented 2 months’ postpartum with significant right sciatic-like back pain. She had no significant past medical history. The symptoms were initially misdiagnosed as a sciatic neuropathy and she was treated symptomatically at another medical center with a good outcome. On examination, she was afebrile and her vital signs were within normal limits. The examination of the abdomen revealed mild tenderness in the right iliac fossa but her obstetric/gynecologic examination was normal. In addition, the examination of the respiratory, cardiovascular, and central nervous systems revealed no abnormalities.

Initial blood tests showed a leukocytosis of 7.3, a hemoglobin of 10.9 g/dL, a raised C-reactive protein (CRP) level of 102 mg/L, and a normal procalcitonin level at 0.316 ng/mL. Serology tests were negative for human immunodeficiency virus (HIV-1 and HIV-2). Spinal lumbar and abdominal computed tomography scans (CT-scan) surprisingly showed a large right psoas abscess measuring 18 × 10 × 8 cm (a volume of about 720 mL) [Figure 1]. However, the right sacroiliac joint, the lumbar spine, and intervertebral disks appeared normal.

Figure 1

Axial abdominal and pelvic CT-scan before (a) and after (b) contrast injection. Sagittal (c) and coronal (d) abdominal reconstructions following contrast administration. There was a large right psoas muscle abscess (stars) displacing the right kidney upward. Note the presence of ring enhancement

Posterior lumbar percutaneous drainage of the abscess was performed. Approximately, 570 mL of purulent fluid was obtained and a drain was left in place [Figure 2a]. Both polymerase chain reaction to detect Mycobacterium tuberculosis and acid fast staining were negative. Culture failed to grow any microorganisms (including mycobacterium and mycoses). She was treated with gentamicin, amoxicillin/clavulanate, and metronidazole parenterally. Her symptomatology improved daily. The follow-up CT-scan on day 2 postoperatively showed near complete resolution of the abscess [Figure 2b]. The drain was removed on postoperative day 4. The patient was discharged to home on postoperative day 15 with combined oral antibiotic therapy (amoxicillin/clavulanate and metronidazole) for 1 month.

Figure 2

Operative view demonstrating posterior percutaneous drainage of the purulent collection above the right iliac crest (a). Follow-up abdominal CT scan 2 days after drainage of the abscess. Note the placement of the percutaneous drain (arrows) and the near complete resolution of the retroperitoneal collection (b). A follow-up axial abdominal CT scan with contrast injection 6 months postoperatively showing the absence of recurrent abscess (c)

Four weeks later, there was no recurrence of neurological symptoms except for mild low back pain. However, a repeat CT-scan of the abdomen and the pelvis showed a re-accumulation of the right psoas collection measuring approximately 400 mL. Subsequently, she underwent a right anterolateral minilaparotomy with a retroperitoneal approach for open abscess drainage. Again, no microorganisms were identified on culture. However, a diagnosis of tuberculosis was established after identification of epitheloid giant cells and caseous necrosis on the fibrotic abscess wall biopsy. The patient made an uneventful recovery and was discharged home on postoperative day 5. A follow-up CT-scan showed no re-accumulation of the abscess. She was successfully treated with antituberculous chemotherapy for 6 months with good clinical and radiological outcomes [Figure 2c].

DISCUSSION

In obstetrical practice, postpartum infection usually involves the uterus and adjacent pelvic structures presenting with typical and predictable symptoms and signs. However, musculoskeletal and focal neurological infections can rarely be seen in the postpartum period.[2316] Among them, PPA is uncommon. Few cases have been previously reported in postpartum patients, typically following normal vaginal delivery or cesarean section [Table 1]. PPA is generally seen in young males without an identifiable cause in most cases. In contrast, secondary psoas abscesses are generally seen in older individuals with chronic diseases.[20]

Table 1

Summary of cases with primary psoas abscess diagnosed during the postpartum period reported in world literature to date

The psoas muscle is in near proximity to anatomical structures such as the thoraco-lumbo-sacral spine, iliac lymph nodes, abdominal aorta, kidneys, ureters, pancreas, jejunum, sigmoid colon, and appendix. For this reason, infections of intra-abdominal organs can spread to the iliopsoas muscle. The important blood supply of this muscle is supposed to predispose it to hematogenous spread from occult sites of infection.[17]

The clinical presentation of a psoas abscess is often variable and nonspecific.[27] The classical clinical triad (fever, back pain, and lower extremity weakness) is present in less than a third of the patients with psoas abscess.[20] As the psoas muscle is innervated by L2–L4, pain can radiate to hip and the lower extremity, mimicking the sciatic nerve symptom of pain. Indeed, there is a direct anatomical link between the psoas muscle and surrounding neural structures (lumbosacral structures) that can produce radicular pain. The diagnosis may be more evident with “psoitis” which is a nonspecific but well-defined sign in patients with psoas abscess. In the supine position, the knee is moderately flexed and the hip mildly externally rotated.[28] Hyperextension of the involved side results in increased leg pain. However, collection of pus in the psoas muscle compartment may present with a gradual onset of symptoms, moderate pain, and low-grade or absent fever, as was seen in our case.

Psoas muscle abscess is often initially misdiagnosed as muscle strain, acute myositis, contusion, hematoma, septic pelvic thrombophlebitis, perinephric abscess, pyelonephritis, acute appendicitis, pelvic or spinal osteomyelitis, trochanteric bursitis, sacroiliitis, cellulitis, or necrotizing fasciitis. In addition, tumors arising from the structures within the pelvis or lumbar area may mimic a psoas abscess.[161723] In the postpartum period, special attention should be given to sepsis arising from endometritis, retained products of conception, or urinary tract infections.[29] In neurosurgical practice, psoas abscess must be considered in the differential diagnosis of low back and leg pain even without the presence of fever.

Laboratory tests reveal nonspecific signs of inflammation: marked elevation of the erythrocyte sedimentation rate and CRP levels, an increased peripheral white blood cell count, and occasionally anemia. Blood cultures may be positive for a particular organism causing the abscess. HIV test is recommended, as this is a cause for immunosuppression predisposing to the development of PPA. In endemic areas, every effort should be made to ensure that the mycobacterium is excluded by acid-fast staining and culture techniques.[625]

CT-scan and magnetic resonance imaging (MRI) are the best radiological modalities for diagnosis because of the low sensitivity and specificity of ultrasound.[413] An obvious systemic source of sepsis should always be considered, with screening for an infectious focus of secondary psoas abscess.[1]

S. aureus is the most frequently identified pathogen in patients with PPA (about 90% of cases). Secondary psoas abscess is usually caused by enteric bacteria such as Streptococcus species (4.9%) and Escherichia coli (2.8%).[20] M. tuberculosis is currently an uncommon cause of PPA and often associated with a concomitant spondylodiscitis (Pott's disease).[1725] Our patient was diagnosed as a primary tubercular psoas abscess since no other source of tuberculosis was identified. If tuberculosis is suspected, etiological confirmation is made either by demonstration of M. tuberculosis on a pathological specimen or histological evidence of epithelioid-giant cell granulomas with caseating necrosis on the biopsy material. DNA amplification techniques and the QuantiFERON®-TB Gold In-Tube assay are also helpful for early and rapid diagnosis.[1]

The pathogenesis of PPA in the postpartum period remains unclear. It has been suggested that trauma during delivery may cause an asymptomatic hematoma within the psoas muscle which can become infected.[81023] Another possibility is the disruption of the sacroiliac joint during delivery that may result in a retroperitoneal abscess.[23] Shahabi et al. found that vaginal or cervical lacerations could potentially spread retroperitoneally causing an abscess.[24] In addition, transient bacteremia following pharyngitis or urinary tract infection may predispose patients to this condition.[1519] On the other hand, alterations to the immune status during pregnancy can lead to impaired cell-mediated immunity with an increased susceptibility to certain infections such as tuberculosis.[3] Our patient had no known history suggesting a malignancy or dysfunctional immunity. In addition, it is unclear as to how a woman who was healthy previously could develop such a potentially serious complication after an apparently uncomplicated vaginal delivery. Furthermore, our patient has no potential risk factors or source of infection for developing a psoas abscess.

Treatment should be started as soon as a clinical diagnosis of psoas abscess is confirmed. The administration of appropriate antibiotics and prompt surgical drainage are necessary when a large suppurative collection is found. Antibiotic coverage should include staphylococcal species and enteric organisms. Antimicrobial adjustments should be based on the report of the abscess fluid culture and sensitivity testing.[12] Antibiotics given for 3–4 weeks are usually sufficient for patients without complications. Tubercular lesions must be treated with the appropriate antituberculous regimens.[13] Drainage of the suppurative abscess collection may be either surgically or under radiological guidance. Percutaneous drainage is much less invasive than open surgical drainage and is appropriate for draining uniloculated and multiloculated abscesses with few septations as was the case in our patient.[9] The indications for open surgical drainage are (1) failure of percutaneous drainage, (2) absence of pathogen identification, and (3) the presence of another intra-abdominal or retroperitoneal pathology requiring surgery. As seen in our patient, it was clear that open surgery was necessary due to the need to identify a causative organism to guide medical treatment. In addition, there are only a very small number of cases treated successfully by antibiotics.[212627]

If treated early and adequately, most patients with PPA will be cured without further complications or recurrent infection.[27] The possibility of another systemic source of infection (multifocal infection) should be considered when the patient does not respond to antibiotic treatment. Fortunately, patients with postpartum PPA usually have a good outcome. However, we must consider that the mortality rate of treated psoas abscess ranges from 6.7% to 8.1%.[1420]

CONCLUSION

PPA is an uncommon but serious clinical entity rarely encountered in neurosurgery, obstetrics, and gynecology. This clinical problem may occur as a postpartum complication but a delay in diagnosis is common because of its insidious development and lack of specific (localizing) symptoms and signs. When PPA is suspected, the CT-scan and MRI help in making an accurate diagnosis and will facilitate the percutaneous or open drainage of the purulent collection. Correct identification of the causative microorganisms and prompt and appropriate usage of antimicrobial therapy can result in improved clinical outcome and reduce neurological morbidity. Therefore, psoas abscess must be considered in the differential diagnosis for patients with low back and leg pain even in the absence of fever.

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Conflicts of interest

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