Urinary System developed from Intermediate Mesenchyme. Intermediate Mesenchyme is disposed longitudinally in the trunk subjacent to the Somites, and on each side of the primitive dorsal aorta and projects in the dorsal wall of the Coelomic and upper thoracic region it shows segments and each segment is known as Nephrotome. Rest of the intermediate mesoderm forms an unsegmented column, known as the nephrogenic cord. (Datta 7^th Edition)¹. Three kidneys – Pronephros, Mesonephros, Metanephros develop in the intermediate Mesoderm in cranio caudal direction Pronephic and Mesonephric kidney are transitory, Metanephric persist as permanent kidney. The metanephric kidney appears last in the Lumbo sacral segments, and persists as the permanent kidney the collecting part of the kidney developed from Ureteric bud and excreatory part from metanephric blastema.

At first the metanephric kidney lies in pelvic cavity opposite the sacral segment. Gradually the kidney ascends and reaches the Iliac Fossa and finally settles in lumbar position between end of 5^th week to 8^th week. Anomalies of the Urinary System are relatively common 3% of live births. Renal agenesis is the absence of one or both kidney. Failure of Ascent of kidney results in a congenital pelvic kidney. Mal development of the ureteral bud and wolffian duct in a developing fetus are thought to be the embryologic causes of an ectopic pelvic kidney^2,3

Sometimes one of the kidney fails to ascend upwards, it may remain in the pelvis. Commonly one kidney will not ascend but rarely two kidneys may remain in the pelvis resulting in both kidneys lying on the same side (Russell et al., 2000)⁴. Sometimes both kidneys may be fused and situated on the same side along the midline. They are known as Crossed fused renal ectopia having incidences of 1 in 1000 live births (Dunnick, 2001)⁵. According to literatures incidence of ectopic kidneys is 1:500 to 1:110 and also incidence of one normal and one pelvic kidney is 1:800to 1:3000 (Gray and Skandalakis, 1972) ⁶. According to Bergman et al., incidences of ectopic kidney are 1:500 to 1:110 followed by incidences of ectopic thoracic kidney 1:13000; solitary kidney 1:1000 solitary pelvic kidney 1:22000 one normal and one pelvic kidney 1:3000 and crossed renal ectopia 1:7000 (Bergman et al., 2009)⁷ . Alternatively, the kidney may fuse together at their caudal poles producing a Horseshoe kidney. (Grays Anatomy). Horseshoe kidneys (HSKs) are the most common congenital renal fusion abnormality, affecting 1 in 500 people anda 2:1 ratio of men to women.^8,9 The horseshoe kidney is the most common genitourinary fusion anomaly, occurring 1/400-1/800 times per 100,000 people [10].

The present study was a Cross Sectional study in Tertiary Care Hospital who were referred to radiology department for CT abdomens. 3500 abdominal CT scans were observed for a period of 6 months. Among those male CT abdominal scans are 2060 and female CT abdominal scans are 1440, from Tertiary care hospital in Andhra Pradesh and observed for renal malformations.

3500 abdominal C.T scans were studied for a period of 6 months. Out of the 3500 ct’s males are 2060 and females are 1440. The results are

Table.1 – Total Number of Renal Developmental abnormalities per 3500 patient.

Table.2 - Percentages of Renal abnormalities in Males & Females

Renal anomalies even though they are rare. But not uncommon, many renal anomalies like Ectopic kidneys, Horse shoe kidneys as they are sometimes a symptomatic or with mild non specific symptoms. So they are accidentally find in most of the cases in the present study, out of 3500 abdominal C.T scan reports, Ectopic kidney was detected in 6 individuals i.e.(0.17 %) and Horse shoe kidney in 8 cases (0.22 %), Malrotated kidney in 8 cases (0.08 %). (Table 1), (chart 1).

In the present study out of 2060 C.T scan reports of males, ectopic kidney was noted in 5 cases (0.24%), (chart 2) and out of 1440 female C.T scan ectopic kidney was noted (0.06 %). Table 2, (chart 3) (Fig 6 & 7) In all above cases the findings were accidentally detected while evaluating Spondylitis, Hernias, Plural Effusion, renal calculi. In the present study a small sized ectopic left kidney in pelvis is associated with situs inversus. factors that may prevent the orderly movement of the kidneys include utreteral bud maldevelopment, defective metanephric tissue, genetic abnormalities, material illnesses or teratogenic causes. In simple renal ectopia, Renal tissue that has not fully ascended to Orhotopic position and remains on its lateral side of which its ureter inserts in to the bladder. The incidence of simple renal ectopia is 1:900. The common clinical issues with renal ectopia is Hydronephrosis due to anomalies of ascension and rotation associated anomalies includes reproductive anomalies in both sexes in appropriate 15% .Renal ectopia can present itself just with abdominal pain & is predisposing situation to pathology in the genitor urinary system. There appears to be, an increased risk of malignancy with an Ectopic kidney. An ectopic kidney is often associated with an increased incidence of stone formation as a result of stasis caused by the altered geometry of urinary drainage. Renal ectopia has a strong association with structure anomalies and the incidence varies from 15%.

In the present study out of 3500 C.T scan reports, we have seen 8 cases of Horse Shoe Kidneys (0.22%). In males 5 cases out of 2060 (0.24 %), (chart 2) and 3 cases out of 1440 (0.2 %). Table 2, (chart 3) (Fig 1 to 5) the incidence of Horse shoe kidney 1:400, Horse shoe kidneys are potential for hydronephrosis & nephrolithiasis, Associated condition include Anorectal malformations, Turners Syndrome, genitourinary malformations. In horse shoe kidney the isthmus may compress the inferior venacava producing sometimes venous edema of lower extremity. On rare occasions it produces ureteric obstruction. The horseshoe kidney has been estimated to be occurring in 0.2% of the general population¹¹ while Flower found horseshoe kidney in 1 in 1000 necropsies and stated that horseshoe kidney is more common in men. Perimutter et al¹² and Basar et al¹³ stated that horseshoe kidney in men is at least two times more frequent than women. The reported incidences of this anomaly in Japan are 0.5%,¹⁴ 0.1%¹⁵ and 0.2%¹⁶ on anatomical dissection. Rarely Horseshoe kidney is prone for injury during blunt trauma to abdomen¹⁷. Malrotated Kidney is the one in which the hylum faces anteriorly or laterally. in the present study Malrotated Kidney was seen in 3 cases (chart 1), (0.08 %), males 1 case (chart 2), (0.04 %), females 2 cases (chart 3), (0.13 %) – Table 2, (Fig 8).

Renal Developmental anomalies are even though uncommon and accidental finding in many radiological investigations a follow up protocol should be maintained in all the subjects as they are prone to conditions such as Reflux hydronephrosis, Nephrolithiasis, rarely Carcinomas & Renal failure. In all most all cases, a thorough evaluation of the patient is of utmost important to rule out serious pathological conditions prior to the arrival of complications, and regular follow up of the patient is to be made mandate. As Horseshoe kidneys is prone to injury during blunt trauma to abdomen, a thorough preoperative urological evaluation is necessary to determine variability in blood supply to formulate an appropriate surgical strategy.

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