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Case Report: Hip Pain in End-Stage Renal Disease

Ilana P. Goldberg, MD, & Samuel Faught, MD  |  Issue: September 2024  |  

Given the concern for septic arthritis, the patient underwent a joint aspiration that revealed only 255 white blood cells, 16% neutrophils, 13,760 red blood cells, and a negative gram stain and culture.

She was subsequently started on vancomycin and piperacillin/tazobactam while results were pending.

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Given the non-inflammatory joint fluid, a diagnosis of erosive azotemic osteodystrophy, rather than osteoarthritis, was ultimately made. Antibiotics were stopped.

In discussion with radiology, findings of articular and periarticular erosions of the left hip consistent with erosive azotemic osteodystrophy had been present on a CT of her abdomen and pelvis performed nine months earlier. Her pain was managed with medications, she was seen by a physical therapist and, ultimately, discharged home.

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Discussion

Our patient had studies conducted as part of an inpatient evaluation, with findings that mimicked a septic joint.

A study by Karchevsky et al. looked at the radiographic findings most commonly associated with septic joints. This study found that MRI synovial enhancement was present in 98% of septic joints, perisynovial edema in 84%, and joint effusions in 70%.2 The findings in our patient included joint effusions and synovitis, as well as periarticular muscle edema, therefore seemingly consistent with a septic joint. She was started on antibiotics, which were quickly stopped based on the sterile joint aspiration.

Ultimately, the patient’s hip pain was attributed to erosive azotemic osteodystrophy. The latest guidelines recommend against radiographic studies as a means of diagnosing erosive azotemic osteodystrophy due to the lack of consistent findings and correlation with clinical symptoms.

SUBTYPES OF OSTEODYSTROPHY
Renal osteodystrophy has traditionally been characterized by the four subtypes, further delineated below. Histology is necessary to distinguish between types because traditional radiography generally cannot reliably do so. An alternative, less-descriptive classification system, the turnover, mineralization and volume system, has also been proposed by the National Kidney Foundation as a way to distinguish histological differences.1
1. Osteitis fibrosa cystica is characterized by excessive osteoclast and osteoblast activity, usually due to excessive levels of parathyroid hormone (PTH). Bone turnover is high, causing disordered collagen formation and bone marrow fibrosis. Subperiosteal resorption and new bone formation around the fingers and clavicles may be suggestive of this subtype.2
2. Contrarily, adynamic bone disease is characterized by low bone turnover due to low PTH levels or resistance to it. Low osteoclast and osteoblast activity leads to decreased bone mineralization and minimal marrow cellularity.3
3. Osteomalacia is characterized by diminished mineralization of bone and may be characterized by either high or low bone turnover. Usually, osteomalacia is associated with elevated levels of PTH. This condition was previously associated with antacids and phosphate binders containing aluminum, which would cause abnormal bone deposits. Use of safer products has made this a rarer subtype.2,4
4. Finally, mixed uremic osteodystrophy represents a combination of osteitis fibrosa cystica and osteomalacia. Bone turnover is high, with hyperactivity of osteoblasts and osteoclasts, but mineralization is abnormal. It is associated with elevated PTH levels.2
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References
1. Moe S, Drüeke T, Cunningham J, et al. Definition, evaluation, and classification of renal osteodystrophy: A position statement from Kidney Disease: Improving Global Outcomes (KDIGO). Kidney Int. 2006 Jun;69(11):1945–1953.
2. Shah A, Aeddula NR. Renal Osteodystrophy. StatPearls. Treasure Island, FL. StatPearls Publishing. 2024. https://europepmc.org/article/NBK/nbk560742
3. Martin KJ, Olgaard K, Coburn JW, et al. Diagnosis, assessment, and treatment of bone turnover abnormalities in renal osteodystrophy. Am J Kidney Dis. 2004 Mar;43(3):558–565.
4. Pierides AM, Edwards WG, Jr., Cullum UX, Jr., et al. Hemodialysis encephalopathy with osteomalacic fractures and muscle weakness. Kidney Int. 1980 Jul;18(1):115–124.

Bone biopsy is the gold standard for making the diagnosis of renal osteopathy and distinguishing its subtype, but is often deferred in clinical practice, with the diagnosis made by trending parathyroid hormone as well as markers of bone turnover, including alkaline phosphatase and C-telopeptide of type I collagen (CTX).3,4 However, radiographic findings associated with renal-related osteodystrophy include periarticular erosions, which may mimic inflammatory arthritis. Joint spaces, however, are generally preserved.4 Most common findings in the sacroiliac joints specifically include poorly defined erosions and articular sclerosis, often symmetrical. These findings were present on our patient’s radiographic studies.5

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