Chronic Right Lower Abdominal Pain Due to Lumbar Ossification of the Posterior Longitudinal Ligament

Abstract

To the Editor: As shown in this case, chronic right lower abdominal pain could be induced by ossification of the posterior longitudinal ligament (OPLL)-evoked damage in the lumbar nerve root. Lumbar OPLL should be considered to be one of the causes of lower abdominal pain. A 46-year-old Japanese man presented to the outpatient department with a 6-month history of right lower quadrant abdominal pain that had worsened over 1 month before presentation. The pain had no relationship to eating or bowel function but often had a relationship to posture. The pain increased when he moved from a supine to a sitting position. He underwent appendectomy when he was 12 years old. His height was 180 cm and body weight was 102 kg (body mass index 31.5). Physical examination revealed severe local tenderness over the right lower quadrant. Carnett's test (1), a clinical test in which abdominal tenderness is evaluated for differentiating abdominal wall pain from intra-abdominal pain, was positive, suggesting that the pain came from the abdominal wall but it was not intra-abdominal pain. Laboratory tests such as white blood cell count, C-reactive protein (CRP, transaminase, lactate dehydrogenase, creatine phosphokinase, lipase, and urine analysis were normal. The patient underwent computer tomography of the abdomen, which showed no abnormal findings in the abdominal cavity (Figure 1). However, computer tomography of the abdomen (arrows in Figure 1a,b) revealed L2–L3 OPLL, which occupied a part of the circumference of the spinal cord (Figure 1). This evidence led us to speculate that the lumbar OPLL might be related to the abdominal pain. As shown in Figure 2, a lumbar X-ray study showed a marked ossification of L2 (arrow) and a coronal computer tomography showed that OPLL was mainly located in the right side of L2 (triangle), which could narrow the right intervertebral foramina, which should pass through the spinal nerve root. The pain was completely relieved after an accurately placed nerve block to right L2 root. From these findings, we diagnosed that the abdominal pain could be induced by OPLL-evoked damage in the right lumbar nerve root. To our knowledge, there is no report describing abdominal pain in association with lumbar OPLL. OPLL is more frequently noted in males and elderly, and is more common in East Asian populations, particularly in the Japanese as in this case. The prevalence of OPLL is highest in Japan, at a rate of 1.9–4.3% (2). OPLL is a multifactorial disease and several gene loci may be involved in the pathogenesis of this disease (3). Although a number of authors have reported on OPLL of the cervical and thoracic spine, few have discussed OPLL of the lumber spine (4). It has been demonstrated that obesity and diabetes mellitus may have a role in the development of OPLL (5). In the present case, his body mass index was 31.5, suggesting that obesity might be involved in the development of OPLL in this case. Okada et al. (6) have reported that out of the 6,127 patients who underwent operations for degenerative lumbar spine diseases during the past 27 years, only 10 patients underwent surgery for lumbar OPLL, indicating that lumbar OPLL is very rare even in Japan. According to their analysis of the 10 patients with lumbar OPLL, unilateral radicular symptoms were most frequently observed and only two patients exhibited typical lumbar claudication caused by the canal stenosis although the rate of maximum canal stenosis brought about by OPLL was relatively high (mean 45.1%) in the 10 cases. These findings suggest that its clinical condition varies greatly among patients depending on the localization and degree of ossification. In fact, the present patient complained of right but not left lower abdominal pain, which could be explained by its unilateral radicular involvement by OPLL. In conclusion, in patients with lower abdominal pain of undetermined cause, OPLL should be considered as a possible underlying disorder.Figure 1.: Computer tomography (CT) of the abdomen showed no abnormal findings in the abdominal cavity but revealed L2 (a: arrow)–L3 (b: arrow) ossification of the posterior longitudinal ligament (OPLL).Figure 2.: A lumbar X-ray study (left panel) showed a marked ossification of L2 into intervertebral foramina (arrow) and a coronal computer tomography (CT) (right panel) showed that ossification of the posterior longitudinal ligament (OPLL) was mainly located in the right side of L2 (triangle).CONFLICT OF INTEREST The authors declare no conflict of interest.