|Year : 2015 | Volume
| Issue : 2 | Page : 349-354
|Intrathoracic kidney in a child with literature review
Abdul-Wahab M Al-Saqladi1, Saleh A Akares2
1 Department of Pediatrics, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen
2 Urology Unit, Department of Surgery, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen
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|Date of Web Publication||3-Mar-2015|
| Abstract|| |
Intrathoracic kidney (ITK) is an extremely rare congenital anomaly, often asymptomatic and discovered incidentally on chest radiography. Diagnosis in children is less frequent than in adults. It affects males more than females and is more common on the left side. Symptoms can be present if it is associated with diaphragmatic defect, herniation of abdominal contents or respiratory compromise. We report a case of a three-year-old boy with right ITK, diagnosed incidentally by chest radiography during treatment of lower respiratory tract infection and confirmed by chest computerized tomography scan.
|How to cite this article:|
Al-Saqladi AWM, Akares SA. Intrathoracic kidney in a child with literature review. Saudi J Kidney Dis Transpl 2015;26:349-54
| Introduction|| |
Intrathoracic ectopic kidney is an extremely rare congenital defect, with about 200 cases published, and the majority of them being in adults.  The prevalence is much lower in children, , and about 39 pediatric cases have been reported since 1985. ,,,,,,,,,,,,,,
Intrathoracic kidney (ITK) is a rare form of renal ectopia, with an incidence ranging from 0.5-5% and a prevalence of one in 10,000 cases of ectopic kidneys.  Thus, the reported incidence is less than five per one million births. This anomaly is rarely bilateral, involves the left kidney more commonly (62%) than the right side (38%) and affects males three times more frequently than females. 
Although ITK is rarely acquired following trauma or surgery,  it is generally congenital and considered to be a sporadic malformation and not associated with an increased risk of recurrence.  Most cases are discovered incidentally on routine chest radiography.  Isolated anomaly is asymptomatic in majority of the individuals and requires no surgical intervention. Symptoms may be present if there is associated diaphragmatic defect and abdominal visceral herniation or when the ectopic kidney is affected by infections, calculi, obstruction or tumor. 
We report a rare case of right ITK in a male child, and the literature on pediatric ITK is reviewed.
| Case Report|| |
A three-year-old male child presented with recurrent respiratory infections. There was no previous history of chest trauma. On clinical examination, he was mildly febrile, with no signs of respiratory distress and, except for occasional rales heard on chest auscultation, other physical findings were non-remarkable.
Laboratory investigations revealed normal hemoglobin level with elevated white blood cells (13,000/mm 3 ) and erythrocyte sedimentation rate. Blood chemistry and urinalysis were within normal limits. A course of antibiotics was administered and his respiratory symptoms were completely resolved. Chest X-ray revealed a mass in the right posterior mediastinum associated with slight elevation of the ipsilateral diaphragm [Figure 1]. A computerized tomography (CT) scan was performed, which confirmed the diagnosis of right ITK [Figure 2]. The patient had no complications and no further treatment was felt to be needed.
|Figure 1: Chest X-ray revealing right posterior mediastinal mass and slight elevation of the right hemi-diaphragm.|
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|Figure 2: Computerized tomography scan of the chest demonstrating the presence of right intrathoracic ectopic kidney.|
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| Discussion|| |
The kidneys are normally formed in the pelvis and, during embryogenic development, they migrate to the upper abdomen. When one or both kidneys are not located in the renal fossae at the retroperitoneal position on either side of the vertebral column it is called renal ectopia. The most frequent sites of renal ectopia are the left pelvic region, followed by the lower lumbar and abdominal cavities.  Intrathoracic ectopic kidney represents a partial or complete renal protrusion above the level of the diaphragm. It is a rare form of renal ectopia and, in the autopsies of 15,919 children, only one case was detected among 22 cases of renal ectopia.  Pelvic ectopia is attributed to failure of the affected kidney to ascend during fetal development, while congenital thoracic kidney is presumed to be caused by accelerated cephalic migration or delayed formation of the diaphragm.  This theory about superior ectopia is recently under dispute as the incidence of associated congenital diaphragmatic hernia is found to be very small (<0.25% of cases).  Therefore, other possible explanations have been postulated, including the influence of the developing adrenal gland and liver on renal position and the co-existence of intrinsic factors in the kidney, such as persistence of the nephrogenic cord.  The final place of the kidney during embryogenesis is determined by the cephalic migration of metanephric blastema and involution of mesonephric tissue in the opposite direction; thus, delay in the involution process leads to extension of the renal development tract and, subsequently, superior malposition.  However, the underlying mechanism seems to be complex and is not fully elucidated. The low frequency of right thoracic ectopia is explained by the early fusion of the pleura-peritoneal channel on the right side and by the presence of the liver as a physical barrier.  Unlike pelvic renal ectopia, which sometimes undergoes obstruction, develops calculi or gets infected, most cases with thoracic kidney maintain normal function and display no dysplastic parenchymal changes.  Nevertheless, some structural abnormalities may be associated, such as deformed shape, rotation anomaly with the hilum facing inferiorly, an elongated ureter, high origin of renal vessels from the thoracic aorta and medial deviation of the lower renal pole.  Other disease processes that affect normally positioned kidneys may also arise later in life. Apart from this, ectopic kidney may be associated with other malformations including the rib and cardiovascular, craniofacial and central nervous systems and gastrointestinal abnormalities as well as chromosomal aberrations such as trisomy 18 and trisomy 21. , Because there is no consistent pattern of these associated anomalies, they should be suspected if a child is symptomatic, has dysmorphic features or the anomaly is detected prenatally.
Intrathoracic ectopic kidneys have been classified into four sub-types with different associations and approach to management: (a) closed diaphragm, (b) eventration of the diaphragm, (c) diaphragmatic hernia, either congenital or acquired and (d) traumatic rupture of the diaphragm. The first two groups are usually asymptomatic, while the other two are often symptomatic and require therapeutic intervention. 
Generally, kidneys can be detected by ultrasonography at 12 weeks of gestation, but intrathoracic ectopia can be overlooked and, hence, prenatal diagnosis is infrequently reported. , ITKs are usually asymptomatic and discovered incidentally during chest radiography. On some occasions, the absence of a kidney on abdomino-pelvic sonography may initiate the search for the missing kidney in the chest cavity. 
Various techniques have been used for the diagnosis of ITK. Plain chest radiography is the first suggested tool and, thereafter, other imaging modalities should be performed to confirm the diagnosis. Ultrasonography, CT scan, magnetic resonance imaging (MRI) and MR-urography are useful diagnostic methods. Ultrasonography has been recommended as a safe, cheap and non-invasive investigation in a well-experienced hand.  Renal scintigraphy is a good tool for the assessment of both functional and structural alterations.  Although ITK is rarely acquired, a history of trauma, which may cause dehiscence, must be excluded. In our case, no such trauma could be found and history of previous operation was entirely denied. The published reports on pediatric ITK since the last reviews of Chong and Chao  and Murphy et al  in 2012 are summarized in [Table 1]. The previous reviews described 23 cases in addition to 16 others included in the current review, altogether contributing to a total of 39 reported cases since 1985 [Table 2]. The 16 new cases included 11 males and five females, 11 were left sided, four on the right and one bilateral and two cases were diagnosed prenatally. Although this analysis was restricted to the pediatric age-group, this result is similar to that reported in a review of cases between 1922 and 1986 carried out by Donat and Donat,  who found a higher frequency in male (63%) than in female patients (37%) and on the left (62%) than on the right side (36%), and 2% were bilateral.
|Table 1: Summary of reported pediatric cases with intrathoracic kidney since 2011.|
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|Table 2: Reported cases of ectopic intrathoracic kidney in children since 1985.|
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There is no consensus on the treatment of ITK, as experience about this clinical entity is limited. In contrast to the previous aggressive surgical approach, more recently, conservative therapy with regular follow-up is advocated for asymptomatic, non-complicated, isolated anomaly.  Surgical treatment is indicated for symptomatic children, mostly presenting with respiratory distress and associated with diaphragmatic defect and herniation of the abdominal contents. In such situations, hernia repair and nephropexy are recommended.
Conflict of interest: None declared.
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Dr. Abdul-Wahab M Al-Saqladi
Department of Pediatrics, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen P.O. Box 6032 Khormaksar, Aden
[Figure 1], [Figure 2]
[Table 1], [Table 2]
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