Retroperitoneal Fibrosis: Unusual Cause of Low Back Pain.

ABSTRACT: Retroperitoneal fibrosis (RPF) is an uncommon collagen vascular disease with a male predominance. Back pain with no specific radiation pattern is common, and bilateral obstructive uropathy, potentially reversible, is frequently associated with RPF. We report a case of RPF and review its diagnosis and management.

LOW BACK PAIN is a prevalent problem in the population and can account for up to 15% of all new outpatient visits. [1] Low back pain is usually a benign condition related to posture or physical strain and generally spontaneously resolves or is easily treated with analgesics, with or without physiotherapy. Therefore, low back pain is often not regarded as a symptom of serious disease. We recently encountered a case of RPF in a 55-year-old man after he had had 6 weeks of low back pain. Clearly, the symptoms of progressive low back pain, increasing malaise, easy fatigability, nausea, vomiting, and reduction in urinary output prompted his coming to our emergency department. Computed tomography (CT) or magnetic resonance imaging (MRI) evidence of periaortic soft tissue mass in this clinical setting, in conjunction with an elevated erythrocyte sedimentation rate (ESR) are consistent with the diagnosis of RPF. [2] However, tissue biopsy and histologic confirmation remain the mainstay of diagnosis. Corticosteroids or other immunosuppressive agents in combination with prompt surgical treatment can lead to remarkable renal salvage and reduction in morbidity.

CASE REPORT

A 55-year-old white man came to our emergency department after 6 weeks of low back pain. He did not think it was anything more than a sprain and took occasional acetaminophen or ibuprofen tablets for temporary pain relief. In the week before admission, he had constitutional symptoms of malaise and vague fevers with anorexia, nausea, and vomiting, and, lately, oliguria. He denied any joint symptoms, rash, or respiratory symptoms. There was a remote history of recurrent gout and the administration of allopurinol for several years. Allopurinol had been discontinued nearly 10 years previously. Hypertension had been controlled with lisinopril, 20 mg daily. He had no history of drug allergies, previous malignancy, abdominal surgical procedures, connective tissue disease, migraine, or intake of any other vascular medications. The patient denied any history of radiation or other unusual chemical exposure.

Physical examination was unremarkable except for limited bilateral basal rales, which improved on coughing, and a mildly swollen scrotum. There was no abdominal distension, and no masses were palpable. No rash was evident, and the musculoskeletal system was intact.

Admission laboratory values were white blood cell count 8.2 x [10.sup.9]/L, hematocrit 37.1%, platelet count 565,000/[mm.sup.5], potassium 5.6 mEq/L, [CO.sub.2] 21 mEq/L, albumin 4.6 g/dL, globulin 4.5 g/L, magnesium 3.7 mg/dL, total calcium 8.8 mg/dL with ionized fraction of 4.04 mg/dL, phosphorus 7.2 mg/dL, serum urea nitrogen (SUN) 56 mg/dL, serum creatinine 10.1 mg/dL, and ESR 74 mm/hr. Urinalysis was unremarkable except for a low specific gravity of [less than]1.005. Electrocardiography showed normal sinus rhythm with no acute changes, and a chest radiograph was unremarkable except for mild hypoinflation. A CT examination of the abdomen and pelvis with oral contrast showed bilateral hydronephrosis and a retroperitoneal soft tissue density encasing the distal abdominal aorta and common iliac arteries (Fig 1).

Subsequently, emergency cystoscopic evaluation with retrograde pyelography showed an anteriorly deviated and inflamed urinary bladder trigone together with multiple obstructing segments in both ureters. Bilateral ureteric J stents were placed in situ (Fig 2), resulting in prompt postobstructive diuresis. Further workup revealed elevated C-reactive protein (CRP) (1:20), positive perinuclear antineutrophilic cytoplasmic antibody (pANCA), and polyclonal elevation of [gamma]-globulin levels on serum protein electrophoresis. Serologic tests were negative for cytoplasmic antineutrophilic cytoplasmic antibody, anticardiolipin antibodies, and antinuclear antibody, and results of urine protein electrophoresis were negative. Furthermore, a retroperitoneal CT-guided fine needle aspiration of the left para-aortic soft tissue fullness showed a dense fibrovascular tissue containing a lymphoid infiltrate and mature plasma cells consistent with RPF.

The patient had an uneventful recovery of renal function with normalization of all electrolyte derangements. Serum creatinine decreased to 1.5 mg/dL and SUN to 18 mg/dL within 2 weeks. Subsequently, bilateral ureteric reconstruction with transposition of the ureters in the retroperitoneal fat was done successfully after recurrence of obstructive uropathy.

DISCUSSION

Idiopathic RPF is an unusual cause of bilateral obstructive uropathy [3,4] Ormond [5] described and named the first case of RPF producing obstruction of the urinary tract and causing renal failure. More than two thirds of patients with RPF have idiopathic disease [3,4] However, RPF is sometimes associated with connective tissue diseases such as polyarteritis nodosa, systemic lupus erythematosus, and rheumatoid arthritis. [6-8] Other causes of RPF include drugs such as methysergide and ergotamine (both agents for treatment of migraine), antihypertensive agents hydralazine and propranolol, infections, inflammatory abdominal aortic aneurysms, trauma, hemorrhage, previous surgery, and retroperitoneal malignancy. [3,9-11]

The finding of hyperglobulinemia in our patient, together with the high ESR, thrombocytosis, positive pANCA, and elevated CRP, may seem to implicate an associated connective tissue disorder. However, these observations are nonspecific and can be seen in idiopathic RPF.[10] As in our patient, early in the syndrome, low back pain may be the only symptom. Weight loss, described in some cases, was not apparent in our patient. Retroperitoneal fibrosis, if unchecked, results in progressive bilateral ureteral obstruction; symptoms of azotemia with oliguria then supervene. Azotemia is found in more than 50% of patients as an initial manifestation, but frank renal failure is much less common. [3,4,12]

The best imaging modalities for the diagnosis of RPF are CT or MRI. [13,14] These techniques not only show the extent and architecture of RPF lesions, but also provide a basis for the assessment of response to therapy. [10] With significant azotemia, CT must be done without contrast medium, and intravenous pyelography (IVP) using contrast medium is contraindicated. Whereas CT and MRI will show the retroperitoneal infiltrative lesion as well as the bilateral hydronephrosis, the IVP shows bilateral hydronephrosis with the classic medial deviation of the ureters, which usually are drawn medially by the fibrotic process. [3,10]

Computed tomographic or MRI evidence of periaortic tissue or a mass in conjunction with an elevated ESR are consistent with the diagnosis of RPF. [2,10] However, the definitive diagnosis of RPF is by biopsy, either CT-guided or, in some cases, open biopsy. The classic histologic finding is collagen bundles interspersed with inflammatory cells, such as macrophages, lymphocytes, and plasma cells. [15] The importance of confirming the diagnosis by biopsy was shown in a case series in which 4 of 16 patients (25%) empirically diagnosed with idiopathic RPF (without initial biopsy confirmation) were subsequently found to have a malignant disease. [16] Attempts have been made to distinguish malignant versus nonmalignant causes of RPF by using MRI and CT. [13,14]

For management, the initial, emergency procedure is often the relief of the obstruction. One modality for this is retrograde cystoscopy with bilateral stent placement, where feasible. Otherwise, antegrade percutaneous nephrostomy may be indicated. Other surgical options are ureterolysis with an effective intraperitoneal transposition, use of ureteral endosplints, wrapping of the ureteric stricture with omentum, ureteric myotomy, ileal interposition, and renal autotransplantation. [12,17] Specifically, in cases of RPF due to inflammatory abdominal aortic aneurysm, aneurysmal resection is the surgical treatment of choice. [11] Immunosuppressive therapy has a role, especially in mild cases or as an adjunct to surgical therapy. Treatment with corticosteroids is the mainstay of medical therapy for RPF. [18] In cases that fail to respond to prednisone, anecdotal evidence exists for the use of azathioprine and tamoxifen. [18-20] Corticosteroids, when used as adjuncts to surgery, lead to a reduction in the incidence of ureteral restenosis. [20] Follow-up CT or MRJ evaluation is usually recommended 6 to 8 weeks after initiating immunosuppressive therapy to assess response to treatment. At the time of this report, our patient was doing well with a serum creatinine level of 1.5 mg/dL.

CONCLUSION

Although nonspecific, the common symptom of low back pain may be the first indication for a serious illness such as RPF. A high index of suspicion in the right clinical setting may lead to early detection and renal salvage.

References

(1.) Silman AJ, Jayson MI, Papageorgiou AC, et al: Hospital referrals for low back pain: more coherence needed. J R Soc Med 2000; 93:135-137

(2.) Jaffer A, Calabrese L: Severe back and abdominal pain in a 44-year-old woman. Cleve Clin J Med 1998; 65:515-518

(3.) Koep L, Zuidema GD: The clinical significance of retroperitoneal fibrosis. Surgery 1977; 81:250-257

(4.) Lepor H, Walsh PC: Idiopathic retroperitoneal fibrosis. J Urol 1979; 122:1-6

(5.) Ormond J: Bilateral ureteral obstruction due to envelopment and compression by an inflammatory retroperitoneal process. J Urol 1948; 59:1072-1079

(6.) Melin JP, Lemaire P, Birembaut P, et al: Polyarteritis nodosa with bilateral ureteric involvement. Nephron 1982; 32:87-89

(7.) Lichon FS, Sequeria W, Pilloff A, et al: Retroperitoneal fibrosis associated with systemic lupus erythematosus: a case report and brief review. J Rheumatol 1984; 11:373-374

(8.) Tsai TC, Chang PY, Chen BF, et al: Retroperitoneal fibrosis and juvenile rheumatoid arthritis. Pediatr Nephrol 1996; 10:208-209

(9.) Elkind AH, Friedman AP, Bachman A, et al: Silent retroperitoneal fibrosis associated with methysergide therapy. JAMA 1968; 206:1041-1044

(10.) Gilkeson GS, Allen NB: Retroperitoneal fibrosis, a true connective tissue disease. Rheum Dis Clin North Am 1996; 22:23-38

(11.) Leseche G, Schaetz A, Arrive L, et al: Diagnosis and management of 17 consecutive patients with inflammatory abdominal aortic aneurysm. Am J Surg 1992; 164:39-44

(12.) Baker LR, Mallinson WJ, Gregory MC, et al: Idiopathic retroperitoneal fibrosis. a retrospective analysis of 60 cases. Br J Urol 1987; 60:497-503

(13.) Degesys GE, Dunnick NR, Silverman PM, et al: Retroperitoneal fibrois: use of CT in distinguishing among possible causes. Am J Roentgenol 1986; 146:57-60

(14.) Arrive L, Hricak H, Tavares NJ, et al: Malignant versus nonmalignant retroperitoneal fibrosis: differentiation with MR imaging. Radiology 1989; 172:139-143

(15.) Mitchinson MJ: Retroperitoneal fibrosis revisisted. Arch Pathol Lab Med 1986; 110:784-786

(16.) Costamire D, Ibrahim G, Robertson C, et al: Clinical parameters and therapeutic outcome in patients with idiopathic retroperitoneal fibrosis. (Abstract). Arthritis Rheum 1991; 34:R34

(17.) Mikkelson D, Lepor H: Innovative surgical management of idiopathic retroperitoneal fibrosis. J Urol 1989; 141:1192-1196

(18.) McDougal WS, MacDonell RC Jr: Treatment of idiopathic retroperitoneal fibrosis by immunosuppression. J Urol 1991; 145:112-114

(19.) Clark CP, Vanderpool D, Preskitt JT: The response of retroperitoneal fibrosis to tamoxifen. Surgery 1991; 109:502-506

(20.) Wagenknecht LV, Hardy JC: Value of various treatments for retroperitoneal fibrosis. Eur Urol 1981; 7:193-200

KEY POINTS

* Low back pain may be the first indication for RPF.

* Idiopathic RPF is an unusual cause of bilateral obstructive uropathy.

* More than two thirds of patients with RPF have idiopathic disease.

* The best imaging modalities for the diagnosis of RPF are computed tomography (CT) or magnetic resonance imaging (MRI).

* Evidence of periaortic tissue or masses in conjunction with an elevated erythrocyte sedimentation rate (ESR) is consistent with a diagnosis of RPF.

* For initial management, emergency procedure is often the relief of the obstruction.

* Corticosteroids are the recommended treatment for RPF.