[MOL] Renal cell carcinoma in an intrathoracic kidney: [00194] Medicine On Line


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[MOL] Renal cell carcinoma in an intrathoracic kidney:



Renal Cell Carcinoma in an Intrathoracic Kidney: Radiographic Findings and Surgical Considerations

William S. Kubricht III, MD, R. Jonathan Henderson, MD, W. Stewart Bundrick, MD, Dennis D. Venable, MD, James A. Eastham, MD, Department of Urology, Louisiana State University Medical Center, Shreveport.

[South Med J 92(6):628-629, 1999. 1999 Southern Medical Association]

Abstract

Ectopic intrathoracic kidney is a rare phenomenon and is usually an incidental finding on a chest radiograph. Of all intrathoracic kidneys, congenital ectopia is most often shown, with a traumatic etiology occurring much less frequently. We report a case of an ectopic intrathoracic kidney with associated renal cell carcinoma. Management, which was based on current treatment recommendations for isolated renal masses, consisted of radical nephrectomy. The patient has been without evidence of disease recurrence for 36 months after surgery.

Introduction

Intrathoracic kidney is a rare form of renal ectopia. In an examination of 15,919 autopsies done on children, Campbell[1] identified 22 cases of renal ectopia, and only one of these was intrathoracic. The following appears to be the first reported case of renal cell carcinoma occurring in an intrathoracic kidney. Modifications to the surgical approach of radical nephrectomy in such cases are discussed.

Case Report

A 77-year-old black man had headache, vomiting, weakness, and excessive thirst for several days. He had a medical history of hypertension controlled by hydrochlorothiazide (25 mg daily). He denied any recent history of trauma. On admission, the patient was found to have a serum sodium value of 122 mmol/L, serum osmolality of 258 mosm/kg, and urine osmolality of 585 mosm/kg. Based on these findings, the patient was admitted for evaluation of the syndrome of inappropriate antidiuretic hormone. Routine chest radiographs revealed blunting of the right costophrenic angle and elevation of the right hemidiaphragm with calcifications (Fig 1). Computed tomography (CT) of the chest and abdomen showed the right kidney and hepatic flexure of the colon to be intrathoracic but subdiaphragmatic. A 3 cm heterogeneous mass of tissue density and with scattered calcifications was noted in the posterior aspect of the right kidney, measuring 54 Hounsfield units. The inferior vena cava was noted to exhibit an anomalous drainage pattern, crossing to the left of the aorta just below the level of the superior mesenteric artery. Because of the location of the ectopic kidney and planned surgical exploration, renal arteriography was done, revealing a normal abdominal aortic origin of a single right renal artery that deviated cranially to supply the right kidney in its ectopic location (Fig 2). In addition, the posterior renal mass was shown to be hypovascular.

Through a right thoracoabdominal incision, the right kidney and colon were found to be located beneath a thin membrane contiguous with the orthotopic diaphragm. A right radical nephrectomy with regional lymphadenectomy was done. Histologic evaluation revealed renal cell carcinoma of the right kidney, grade II, stage T2 N0 MX. The patient's postoperative course was uneventful. The serum sodium level returned and remained within normal limits. Three years after operation, the patient has normal serum electrolyte values and has no evidence of recurrence of the malignancy.

Discussion

Intrathoracic kidneys have a reported prevalence of less than 1 in 10,000 and represent only 5% of ectopic kidneys.[1-3] Left-sided ectopia is more common, and men are affected three times more often than women.[4] High ectopia is usually not associated with functional abnormality and is more commonly an incidental finding on chest x-ray.[5] Four forms of intrathoracic ectopy have been reported. Most commonly, as was found in our patient, a thin membrane of diaphragm will cover the kidney, thus making it subdiaphragmatic yet intrathoracic in position.[2,6] This is also referred to as a diaphragmatic eventration.[4] The embryologic origin is debatable; various authors have proposed either an abnormality in pleuroperitoneal membrane fusion or abnormally high migration of the kidney due to delayed mesonephric involution.[7] Traumatic rupture of the diaphragm, Bochdalek's hernia, and supradiaphragmatic ectopic kidney without herniation are less common causes of an intrathoracic kidney.[2] Anatomically, four features are commonly found: rotational abnormality, in which the hilum is anterior; elongated ureter; high renal vessel origin; and medial deviation of the lower pole.[8] The adrenal gland may or may not be ectopic.[2] Our patient had an elongated ureter, anterior hilum, and medially deviated lower pole.

The possibility of an intrathoracic kidney exists with all chest masses, though its likelihood is low. Inappropriate secretion of antidiuretic hormone may be present with any pulmonary lesion, though our patient may have had a paraneoplastic syndrome associated with renal cell carcinoma. In this case, development of a renal neoplasm was likely coincidental to its intrathoracic location and is extremely rare, with no known documented cases in the literature. This case supports inclusion of an intrathoracic kidney in the differential diagnosis of an asymptomatic chest mass. Ectopic kidneys should be screened no differently from orthotopic units to rule out neoplasm when indicated. Historically, excretory urography has been used to evaluate renal masses, but currently contrast-enhanced CT is the standard for evaluating renal masses. Since this is the first report of an intrathoracic kidney harboring renal cell carcinoma, we do not believe evidence exists to suggest an altered incidence of tumor development in orthotopic kidneys, and one should direct further studies according to signs and symptoms.

Reprint requests to James A. Eastham, MD, Louisiana State University Medical Center, Department of Urology, 1501 Kings Hwy, Shreveport, LA 71130.

References

  1. Campbell MF: Renal ectopy. J Urol 1930; 24:187-189
  2. Donat SM, Donat PE: Intrathoracic kidney: a case report with a review of the world literature. J Urol 1988; 140:131-133
  3. Sumner TE, Volberg FM, Smolen PM: Intrathoracic kidney. diagnosis by ultrasound. Pediatr Radiol 1982; 12:78-89
  4. Grosfeld JL: The biological basis of modern surgical practice. Pediatric Surgery, Textbook of Surgery. Philadelphia, WB Saunders Co, 1991, 14th Ed, pp 1149-1186
  5. Ramus AJ, Slovis TL, Reed JO: Intrathoracic kidney. Urology 1979; 13:14-19
  6. Paul AT, Uragoda CG, Tayewardene FL: Thoracic kidney with report of a case. Br J Surg 1960; 47:395-397
  7. Angulo JC, Lopez JI, Vilanova JR, et al: Intrathoracic kidney and vertebral fusion: a model of combined misdevelopment. J Urol 1992; 147:1351-1353
  8. Lozano RH, Rodriguez C: Intrathoracic ectopic kidney: report of a case. J Urol 1975; 114:601-602