Int J Anat Res 2016, 4(4):3263-66. ISSN 2321-4287 3263

Case Report

SPLIT KIDNEY: A CASE REPORTCaio Fernando Cardoso Souza, Lucas Alves Sarmento Pires *, Alvaro de RezendeTeixeira, Rogério Carvalho de Araújo, Marcio Antônio Babinski.

ABSTRACT

Address for Correspondence: Lucas Alves Sarmento Pires, Fluminense Federal University, RuaProfessor Ernani Mello, 101, São Domingos - Niterói - Rio de Janeiro - Brazil ZIP CODE 24210-150.Phone: +55 (21) 98307-6012 E-Mail: lucaspires@id.uff.br

Background: The kidneys are retroperitoneal organs with a unique embryological formation. They are formed bytwo distinct embryological bases, one for the collecting system and one for the parenchymatous tissue. Thekidneys are often target to anatomical variations regarding its vessels, its collecting system, its position on theabdominal cavity and others. Most of those variations happen due to different stimuli during its embryonicdevelopment. Such is the case of the distinct fetal period lobulation, which happens uncommonly. Many of theseabnormalities may produce clinical symptoms, moreover, variations can cause confusion among cliniciansregarding diagnostic aspects or surgeons during partial nephrectomy, kidney transplants and other surgicalprocedures involving the retroperitoneal area or the kidney itself.Case Report: During regular dissection of a male cadaver, after dissection of the retroperitoneal region, it wasobserved an abnormal conformation of the right kidney: it was completely divided by a fibrous septum into twolobes. The fibrous septum was composed of the same tissue of the kidney’s fibrous capsule. A coronal section ofthe kidney showed that there was also a variation regarding the calyces: they joined independently in order toform the renal pelvis.Conclusions: We believe that knowledge regarding variations of the kidney is of great significance to the clinicianand the surgeon, and many of them can produce discomforting symptoms.KEY WORDS: Anatomic Variation, Kidney, Retroperitoneal, Embryology.

INTRODUCTION

International Journal of Anatomy and Research,Int J Anat Res 2016, Vol 4(4):3263-66. ISSN 2321-4287

DOI: http://dx.doi.org/10.16965/ijar.2016.455

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DOI: 10.16965/ijar.2016.455

Received: 31 Oct 2016Peer Review: 01 Nov 2016Revised: None

Accepted: 01 Dec 2016Published (O): 31 Dec 2016Published (P): 31 Dec 2016

Anatomy Laboratory, Morphology Department, Fluminense Federal University, Rio de Janeiro, Brazil.

lobulated kidney in fetal period [1,2].Variations and anomalies regarding this organare well established and described in the litera-ture by many authors [1-4]. Anomalies andvariations are more commonly found on thevessels of the kidney, although the renalarteries are less susceptible to variations thanthe veins [1,3-5].Knowledge of such variations is crucial toidentify diseases and is the key to a successfulsurgical procedure, such as partial nephrectomy.

The kidneys are retroperitoneal organs thatproduce and excrete urine. In this fashion, theyare in charge of eliminating most of the toxicresidues of our body. Situated at each side ofT11-L3, the kidneys are surrounded by fat tis-sue and loose connective tissue. The right kid-ney is usually situated more inferiorly than theleft, due to the large size of the liver [1,2]. Thekidneys are enveloped by a fibrous tunic, andfissures may be found in infants, remnants of a

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Souza CFC et al. SPLIT KIDNEY: A CASE REPORT.

Furthermore, interpretation of ultrasound andother imaging exams requires awareness of themany different types of variation [2,6].We report a case of an uncommon variationregarding complete division of the right kidneyin two distinct lobes and review the embryologi-cal aspects of the kidneys, while performing areview of the literature and addressing itssurgical and clinical significance.

CASE REPORT

kidney. After removing the pararenal adiposetissue, we saw that the right kidney wascompletely segmented from its anterior to itsposterior faces (Figure 1). We also observed thathe fibrous capsule that envelops the kidney wasalso reflected, thus, causing complete divisionof the right kidney into two distinct lobes. Acoronal incision was made from its lateralmargin to the medial margin, and we alsonoticed that independent calyxes joined inorder to form the renal pelvis (Figure 2). Thevasculature showed extrarenal vessels to eachindependent pole.

Fig. 1: The septate kidney. An anterior view of the rightkidney shows its complete septation into two dystinctlobes.

Fig. 2: Coronal section of the right kidney. We can seethat the calyces arise from each lobe independetely inorder to form the renal pelvis. The fibrous septa canalso be seen.

A male cadaver fixed with a 10% formalinsolution was dissected during regular anatomylessons of the Fluminense Federal University’sanatomy laboratory. While dissecting theretroperitoneal portion of the abdominal cavity,we observed an unusual display of the right

DISCUSSION

The kidneys are developed together with otherorgans of the urogenital apparatus through 3pairs of structures that develops in acraniocaudal disposition from the intermediatemesoderm: the pronephros, the mesonephrosand the metanephros. The definitive kidneys arederived from the metanephros [2,6,7].During the fourth week of development, a smallduct (mesonephric duct or Wolffian duct) isgenerated through epitelization of the interme-diate mesoderm. Those ducts form a smallconglomerate of cells which regresses to giverise to the mesonephros. Then, mesonephrictubules begin to develop within mesonephricbuds adjacent to the mesonephric duct oneither side of the vertebral column, in a cranio-caudal direction, as they differentiate, thecranial tubules regresses, and this structure onlyoccupies the region between L1-L3, and startfunctioning as an abbreviated version of thedefinitive kidney until the tenth week, ceasingtheir role, regressing in females and they arethought to give rise to the efferent ductules inmales [6,7].The metanephros is composed by two differentportions: excretory and collector, which havedifferent embryological origins. Two uretericbuds arise from the caudal portion of themesonephric duct (day 28), then, they penetratethe metanephric mesenchyme and begin tobifurcate and replicate, branching itself. Afterthe sixteenth week, they form around fourteento sixteen lobes, giving the metanephros alobulated aspect [6,7]. This process continuesand the ureteric bud expands to form the renal

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pelvis, then it bifurcates four times to form themajor calyces, and around the seventh week theminor calyces are formed through the samemechanism. In 32 weeks, this process formsthree million of collecting ducts [6,7]. In fishesand amphibious, the kidney is formed by themesonephric bodies, while in reptiles, birds andmammals they suffer atrophy and disappear [2].The normal kidney is formed from fusion ofmultiple lobes known as renunculi or reniculiwhich develop during the second trimester.Those ranunculi are constituted by a largecentral medullary pyramid containing thecollecting tubules surrounded by cortex contain-ing the glomeruli [6].The kidneys are developed in the pelvis, and thenmigrate to the upper portion of the abdomen.As they arise, their blood supply from the exter-nal and internal iliac vessels regresses and theabdominal portion of the aorta takes main rolein its supply. Furthermore, the kidney hilum isfaced ventrally, and as they ascend, this hilumrotates medially in an angle of 90° degrees. Theyattain their adult position by the ninth week[7,8]. Understanding the embryological aspectsof the kidney is essential to comprehend itsnormal and pathologic variations [7].According to Goss (1973) mammals such as thebear and the ox display a kidney with manydistinct lobes, although this feature in humansis only present during the fetal period of devel-opment [2]. Moore and Dalley (2001) report anincidence of 7% of this condition in adults [9]As previously stated, the kidney is formed by ajunction of many ranunculi. The lobulatedaspect of the kidney is normal in neonates, andthe organ possesses many grooves. As thekidney develops, this lobulated aspect regressesand takes the regular aspect [7]. A failure in thejunction mechanism of two larger lobes wouldexplain our variation, as the capsule also invagi-nates to form two distinct lobes, similar to thevariation of the lungs, whereas the azygos veinarches over the hilum and together with thepleura a new lobe is formed on the right lung,the azygos vein lobe [10]. Moreover, Rodriguez(2014) described that persistent fetal lobulationmay be related to defects in renal maturation[11] A review of the literature shows many varia-

tions of the kidney: they may be longer or nar-rower [3]; one kidney may smaller or absent,while the other is proportionally hypertrophied[1,3]; a supernumerary kidney may be found[1,2]; it may present the horseshoe kidney con-figuration [2,3]; it may present the form of a ringwhen both poles of both kidneys are joined [1,2];the kidneys can suffer malrotation [8]; ectopickidneys have been described located more cra-nially [2]; on the iliac fossa [2]; over the sacro-iliac joint [2]; over the sacral promontory [2]; onthe pelvis [2,3,12]; between the rectum and thebladder or even laterally to the uterus [2]. Fur-thermore, the kidney may “float”, which wouldbe caused by the complete involvement of thekidney by the peritoneum, and finally, the kid-ney may be mobile, a condition more known inmalnourished males [2,3]. Nevertheless, varia-tions of the calyces, pelvis and ureter are alsocommon and extensively described in the litera-ture [3,13].Abeshouse (1944) reported a similar case toours, where the left kidney was completely di-vided into two lobes with a distance of 3 cmfrom each other, due to the presence of a sep-tum [14].Most of these variations are presented togetherwith anomalies of supernumerary vessels andcongenital defects of the ureter, thus, some mayor may not cause a great number of symptomssuch as hydronephrosis, infections and nephroli-thiasis, and may lead to hypertension, although,further studies are needed to prove this hypoth-esis [5,8,15]. Persistent fetal lobulation may beassociated with syndromes such as Bardet-BiedlSyndrome or may be confused in exams byrenal scars, schwannomas, hemangiomas, andangiomyolipomas [11,16-19].

CONCLUSIONIn conclusion, knowledge of the many kidneyvariations and its associated structures are ofgreat importance to the surgeon and physician,as renal transplants, partial nephrectomies,lithotripsies and other procedures are common.Furthermore, in order to understand the clinicalaspects of many diseases and to avoidmisdiagnosis, knowledge regarding the kidneydevelopment and possible failures should befurther studied.

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Conflicts of Interests: None

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How to cite this article:Souza CFC, Pires LAS, Teixeira AR, Araujo RC, Babinski, MA. SPLITKIDNEY: A CASE REPORT. Int J Anat Res 2016; 4(4):3263-3266.DOI: 10.16965/ijar.2016.455