Supernumerary thoracic ribs.

Abstract

SUPERNUMERARY RIBS are uncommon. When present they usually arise from cervical or lumbar vertebrae, although sacral, coccygeal, intrathoracic, and aberrant lumbar ribs have also been reported. This paper concerns a patient who has 15 pairs of thoracic ribs arising from 15 thoracic vertebrae. In our search of the literature we have not found another case of a patient with this many pairs of thoracic ribs. The patient, a 35-year-old Caucasian man, was admitted for the first time to the University of Michigan Medical Center for an ileostomy to establish fecal control. A subtotal colectomy with an ileoproctostomy for Hirschsprung's disease at age thirty had been performed five years previously. Since then he had experienced persistent diarrhea and fecal incontinence. His history also included incision of a membranous imperforate anus shortly after birth. He had no complaints referable to his chest or back, and no structural abnormalities were evident on physical examination. The preoperative chest roentgenogram showed 15 pairs of well developed thoracic ribs arising from 15 thoracic vertebrae (Fig. 1). Roentgenograms were then obtained of the entire spine. There were seven cervical vertebrae with multiple congenital malformations including posterior fusion of the bodies of the second and third cervical vertebrae and numerous areas of fusion between the facets of the cervical vertebrae (Fig 2). There were five lumbar vertebrae with spina bifida occulta of the first vertebra. The first sacral vertebra showed hy-persegmentation, and the lower sacrum was deficient on the right side with a wide sacral hiatus (Fig. 3). Intravenous urography showed a 2 cm cyst in the right kidney which communicated with the right upper pole calyx. The right kidney was slightly smaller than the left. Comment The incidence of rib anomalies is not greater with Hirschsprung's disease or with imperforate anus, although there is a higher incidence of vertebral and genitourinary anomalies with the latter (1). Cervical ribs may produce neurologic and vascular symptoms, but lumbar ribs are usually of clinical significance only in differential diagnosis from a fracture of a transverse process. Lumbar ribs most commonly arise from the first lumbar vertebra, although they have been reported to arise from the second (6) and third vertebrae (3). Bettenhäuser reported a case of an aberrant rib in the lumbar area overlying the right ilium which was was not connected to the vertebral column (2). Rudimentary ribs have also arisen from the sacrum (4) and coccyx (5). In our patient the supernumerary ribs were normal in appearance and position and arose bilaterally from the three extra thoracic vertebrae. Embryologically, this is understandable as vertebrae and ribs have common origin and parallel development from sclerotomic mesenchyme.