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
- Campbell MF: Renal ectopy. J Urol 1930; 24:187-189
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- Sumner TE, Volberg FM, Smolen PM: Intrathoracic kidney. diagnosis by
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- Grosfeld JL: The biological basis of modern surgical practice. Pediatric
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1149-1186
- Ramus AJ, Slovis TL, Reed JO: Intrathoracic kidney. Urology 1979; 13:14-19
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