Joel I. Sarachek, M.D.

Introduction

An estimated 10-15 million Americans are currently infected with dormant tuberculosis (TB), and more than 17,000 cases of active disease were reported to the CDC in 1999. TB rates in Los Angeles are high compared to most U.S. cities because of the large population of people in high-risk categories for harboring the disease, therefore, primary care physicians should be vigilant to diagnose and treat TB.¹

Most active TB is confined to the lung, but approximately 15% is extrapulmonary. The most common types of extrapulmonary TB are, in descending order of frequency, pleural, lymphatic, bone and joint, genitourinary, miliary disease, meningitis, and peritonitis.² The classic symptoms of pulmonary TB are well-known and fairly easily recognized: persistent cough with or without sputum and/or blood, fever, sweats, chills, anorexia, weight loss, and malaise. Extrapulmonary TB may be associated with many symptoms, often very mild and indolent, such as microscopic hematuria, mild malaise, or back discomfort.

Case Report

A 42-year-old Hispanic female born in Mexico but living in the US since 1980, presented at her initial office visit stating that she had not been feeling well for the past week. She had worsening headache with nausea and emesis for three days. An examination at work showed her blood pressure was elevated, so she was instructed to see a doctor. She had no previous history of hypertension and other past medical history was negative. She had no known contacts with anyone with TB, HIV, chronically ill or with other TB risk factors. She had experienced headaches over the past year and noted an approximate twenty-five pound weight loss over three months associated with malaise. She denied fevers, chills, sweats, anorexia, visual change, chest pain, cough, shortness of breath, abdominal pain, back pain, other neurologic complaints, or complaints relating to the genitourinary or musculoskeletal systems.

Her blood pressure was 220/115, pulse 100, temperature 99, and weight 130. She was alert and oriented, verbal, pleasant, but uncomfortable holding her head. Her skin was warm and dry with normal turgor and no lesions. Her HEENT exam was unremarkable without papilledema and a cup to disc ratio of 0.4. Neck was supple with no adenopathy orthyromegaly. Lungs were clear to auscultation. The heart was slightly tachycardic with normal S1 and S2, and no murmur, gallops or rubs. Breast exam had no masses and there was no axillary adenopathy. Genitourinary, rectal and neurological exams were unremarkable; chest X-ray was negative. The abdomen had normal bowel sounds, was soft, non-distended and was slightly tender with fullness in the left lower quadrant from the umbilical level to the pelvic brim, without guarding or rebound. Her back was not tender to percussion and with palpation there was no muscular or spinous process tenderness. The patient was given an oral blood pressure medication and sent to the emergency room for blood pressure control and monitoring. In the ER, the head CT and a chest X-ray were normal and the patient was given I.V. antihypertensive medication. The patient was discharged with lower blood pressure and lessened headache.

Her blood pressure was now well controlled, however, the abdominal and pelvic CT scans revealed a psoas muscle larger on the left than the right due to small areas of rounded fluid density, with peripheral enhancement, identified from the level of the umbilicus extending inferiorally toward the pelvis. The largest psoas abscess was approximately 2.5 cm in maximum dimension. The retroperitoneal and mesenteric fat adjacent to the psoas muscle maintained a normal density without evidence of infiltrative abnormality. No gross abnormality of the left kidney or ureter was present to suggest genitourinary source, and the bone density adjacent to the left psoas muscle was normal with no gross evidence for infectious spondylitis.

Because of the small size of the abscess, CT guided needle aspiration without need for percutaneous catheter drainage was felt to be appropriate, and 15 cc's of straw colored purulent fluid was drained from the abscess. The immediate fluid analysis showed negative gram stain, fungal stain, AFB smear and cytology. Two weeks later, the culture for Mycobacterium tuberculosis returned positive while all other cultures were negative.

The patient was treated with the standard protocol. For the first two months, she received isoniazid, rifampin, pyrazinamide, ethambutal, and supplemental pyridoxine. The patient received regular monitoring and liver function tests for potential side effects. After two months, the patient gained six pounds, had no abdominal pain, and the sensitivities returned, indicating no drug resistance. The regimen was reduced to isoniazid, rifampin, and pyridoxine for one year. Her total weight gain after one year was twenty pounds. Repeat of abdominal and pelvic CT scans showed a normal appearing psoas muscle with interval resolution of the psoas abscess.

Discussion

Psoas abscesses (TB and pyogenic) are not common; in the U.S., as few as twelve cases are presented per year.³ In the pre-antibiotic era, TB was the predominant pathogen causing psoas abcess.⁴ TB was found to be the predominant cause of psoas abscess in a thorough review, published in 1961, of the previous fifty years of surgical experience at one United States center. Since that time, tuberculosis psoas abscess has become quite rare in this country. A case series spanning 1985-1990 found two of eleven patients to have tuberculosis psoas abscess, whereas a twenty-eight year retrospective review ending in 1989 found only one patient in a series of sixty-seven with TB being the causative agent of psoas abscess. There were only five reports of psoas abscess secondary to TB published in the North American literature in the years 1990-1993.⁵ Tuberculosis psoas abscess is still usually due to complicated spinal tuberculosis (Pott's Disease), but it can be due to direct extension from other adjacent structures or from hematogenous seeding. However, the occurrence of tuberculosis psoas abscess as a presenting manifestation of TB without evidence of active infection elsewhere has seldom been reported. A case report from Spain in 1998 claimed to be only the fourth case of tuberculosis psoas abscess reported in the Medline archives between 1981-1996. In this case, a 4 cm abscess had 100 cc's drain via percutaneous catheter over four days.⁴

Much of the current data on tuberculosis psoas abscess and its management comes from India where it is still quite common. One case study found twenty-seven of forty-one psoas abscesses were due to TB, with the authors commenting that most of these were the result of spinal TB.⁵ In another study over a five-year period containing fifty-six psoas abscesses in fifty-one patients (twenty-seven had TB, bilateral in five, and twenty-four pyogenic), 74% of the tuberculosis psoas abscesses were secondary to spinal TB. Percutaneous drainage was initially successful in all twenty-seven patients with tuberculosis psoas abscess. However, eight patients presented requiring repeat intervention. Therapeutic needle aspiration was done in three of twenty-seven, generally those with small abscesses (less than 5 cm), and two of the three had recurrence within two months and were managed successfully with repeat needle aspiration. Of the twenty-four who underwent percutaneous catheter drainage (average eleven days), six presented with recurrence between two and sixteen months later.⁶ Another study of fourteen psoas abscesses (ten pyogenic and four TB) showed that percutaneous treatment (either needle aspiration for small abscesses or percutaneous catheter drainage for large abscesses) is less invasive but an equally effective alternative to surgery.⁷

Conclusion

As in this case, psoas abscess presentation may be subtle and non-specific, and present a diagnostic challenge. This patient's complaints were of headache with nausea, vomiting, general malaise and weight loss, and denial of any pulmonary, back, or abdominal symptoms. Evidence of the psoas abscess was found in the laboratory and radiological studies performed. There was no evidence of tuberculosis in the spine or any other tissues, hence, this may be a rare case of primary tuberculosis psoas abscess. Fortunately, the patient had small abscesses, the largest being 2.5 cm; she was successfully treated with percutaneous needle aspiration and excellent compliance with one year of anti-tuberculosis medication.

REFERENCES

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