Embriologic abnormalities often occur in the lung. We present a case of an unusual intrathoracic mass.
A 34 year-old man with no significant past medical history presented to the emergency room with dyspnea that started three days before. He had fever, chills and a cough productive of yellow sputum. There was no history of chest or abdominal trauma. The physical examination revealed a 34 year old man in no acute distress, having low grade fever (100.8F). The chest examination showed no signs of consolidation or wheezing. The abdominal exam didn’t reveal any organomegaly or hernia. The rest of the examination as well as the CBC and chemistry were within normal limits. The presumptive diagnosis was pneumonia. A chest roentgenogram revealed a right lower lobe well defined mass contiguous to the right hemi-diaphragm. (fig.1). Computer tomogram with intravenous contrast was performed. (fig.2) The patient was treated with oral antibiotics for 5 days after he was discharged from the emergency department. He was seen in the pulmonary clinic for a follow up two weeks at which time he was asymptomatic.
The computer tomogram of the chest showed a right intrathoracic ectopic kidney. The contrast substance was taken up and excreted by the ectopic kidney. The kidney appeared to be functional with no signs of obstructive uropathy. During fetal life the kidneys form from the metanephros in the pelvis. The hilum of the new kidney faces anteriorly. During the fifth or sixth week of gestation the kidneys begin to migrate caudally and rotate so that by week 9 the kidney are usually at the L1 level and the hilum are now facing antero-medially. An abnormally high ascent of the metanephros will generate a diaphragmatic defect and subsequently an ectopic kidney in the thorax. If the kidney does not ascend at all a pelvic or horseshoe kidney results. Intrathoracic ectopic kidneys may be congenital or acquired. This condition is rarely bilateral and occurs mostly on the left side. There is a marked preponderance in males (4,5). True intrathoracic ectopic kidney presents during fetal life and has four characteristics: 1) rotation anomaly, 2) long ureter, 3) anomalous high derivation of the renal vessels from the thoracic aorta, 4) medial deviation of the lower pole of the kidney (4). The etiology of true ectopic kidney is not well known. Acquired intrathoracic ectopic kidney occurs due to a diaphragmatic hernia that may be caused by a congenital diaphragmatic defect, in which case the vascular pedicle has a normal morphology. It can also be caused by trauma. In most cases it is asymptomatic. The diagnosis of intrathoracic kidney is one of the unusual causes of mediastinal mass on chest roentgenogram and is confirmed by intravenous urography (1,3), or computer tomography (1). Based on literature review, the incidence of intrathoracic ectopic kidney is very low. Almost 60 cases have been reported. Apart from its rare complications such as respiratory distress in newborn babies, this anomaly does not require any specific treatment (2).
Although this is a rare condition, the presence of an intrathoracic mass needs to be carefully evaluated before performing invasive diagnostic procedures.
m.e. iliescu, None.