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  1. The adrenals are embryologically and functionally distinct from the kidneys, thus in cases of renal ectopia, the adrenals are found at its normal location. Q
  2. In the normal adults weighs approx. 35 gm. & measures 3-5 cm. in greatest dimension.
  3. The right gland is pyramidal in shape while left one in crescentic and rests more medal to the upper pole.
    The right adrenal thus lie more superior than the left adrenal.
  4. Each adrenal has two separate distinct elements; CORTEX AND MEDULLA.  The central medulla consists of chromaffin cells derived from the neural crest. It is closely related to the sympathetic nervous system.
  5. The adrenal cortex is mesodermally derived and forms the bulk of the gland; 80-90%. Cortex consists of (GFR) Zona glomerulosa, which produces aldosterone in response to rennin Q
  6. Angiotensin system; Zona fasciculata and Zona reticularis, which produce glucocorticoids and sex steroid respectively.     
  • Vascular supply:
  1. Each adrenal is supplied by three arteries and one vein:
    Superior branches from inferior phrenic. Q
    Middle branches from the aorta.
    Inferior branches from the ipsilateral renal artery.
  2. A single large vein exits from the adrenal hilum and drains into the IVC on the right side and renal vein on the left side.
  3. The adrenal lymphatic drain into the para-aortic lymph nodes.
  4. The adrenal cortex is believed to receive no innervations.
Embryology Of The Genitourinary System
The nephric system develops progressively from 3 distinct entities:          
  1. Pronephros:
    1. It is the earliest nephric stage and extends from 4th to 14th somites and consists of 6-10 pairs of tubules.
    2. It disappears completely by 4th week.
  2. Mesonephros:
    1. It is the principle excretory organ during early embryonic life (4-8 weeks). Q
    2. Though it gradually disintegrates, part of its duct system forms male reproductive organ.
    3. In mesonephros, primitive glomeruli are present.
    4. Its primary nephric duct is called mesonephric duct, and it opens distally into the cloaca.
  3. Metanephros:
    1. It originates both from mesonephric duct and intermediate mesoderm.
    2. It forms the main kidney, while a ureteral bud (a branch of mesonephric duct) forms ureter, pelvis and collecting duct.
    3. Main features of development are:
      1. The 3 successive units of the system develop from the intermediate mesoderm.
      2. The tubules of all levels appear as independent primordial and only secondarily unite with the duct system.
      3. The nephric system is laid down as the duct of the pronephros and develops from the union of the ends of the anterior pronephric tubules.
      4. The pronephric duct serves later on as mesonephric duct and gives rise to ureter.
      5. The embryonic ureter is an outgrowth of the nephric duct, yet the kidney tubules differentiate from the adjacent metanephric blastoma.
Anomalies of The Nephric System
  1. Failure to ascend leads to ectopic kidney (1 in 1000). An ectopic kidney may be on the proper side but low (simple ectopia), or on the opposite side (crossed ectopia), with or without fusion.
  2. Failure to rotate during ascent causes malrotated kidney.
  3. Fusion of the paired metanephric masses leads to various anomalies; most common of which is horseshoe kidney.
  4. The ureteral bud from the mesonephric duct may bifurcate, causing bifid ureter. An accessory ureteral bud may develop from the mesonephric duct, thereby forming a duplicated ureter. Rarely such bud has a separate metanephric mass resulting in supernumerary kidney.
  5. Lack of development of a ureteral bud results in a solitary kidney and a hemitrigone.  (Renal agenesis = 1: 1400)
  6. In the double ureteral buds, the main ureter bud, which is first to appear, drains upper moiety and is more caudal on the mesonephric duct, reaches the bladder first. It then moves upwards and laterally. The 2nd bud is more caudal in bladder. The double ureter always cross (Weigert-Meyer Law).
Horseshoe Kidney
  1. Horseshoe kidney occurs in from 1 in 800-1000 live births. It is twice as common in males
  2. The horseshoe kidney is the most common type of renal fusion anomaly. Q
  3. It consists of 2 distinct, functioning kidneys on each side of the midline, connected at the lower poles by an isthmus of functioning renal parenchyma or fibrous tissue. Isthmus in front of abdominal aorta. 
  1. Pathophysiology:
    1. The horseshoe kidney does not by itself produce symptoms.
    2. There are higher rates of hydronephrosis stone formation, infection. Q
    3. The most common associated finding in horseshoe kidney is ureteropelvic junction obstruction.
    4. It causes the majority of problems. Obstruction is due to the high insertion of the ureter into the renal pelvis. Q The crossing of the ureter over the isthmus may also contribute to obstruction.
  2. Clinical:
    1. Usually Asymptomatic
    2. Horse shoe kidney is an incidental finding during radiological examination.
    3. Most common associated finding is ureteropelvic junction obstruction & it causes most problems.
    4. Nearly one-third of patients with a horseshoe kidney remain asymptomatic. Q
    5. Symptoms, when present, are usually due to obstruction, stones, or infection.
    6. Other associated anomalies with HS kidney are Ureterocele, VUR, ureteral duplication, hypospadias or undescended testis, polycystic kidney disease, turner syndrome.
    7. In children urinary tract infection and in adults, pain is the most common presenting symptom. Q    
  3. Relevant Anatomy:
    1. The kidneys may be lower than normal as the isthmus is tethered during renal ascent by the inferior mesenteric artery.
    2. The isthmus usually lies anterior to the great vessels at the level of the 3rd-5th lumbar vertebra. Q
    3. The vascular supply is variable and originates from the aorta, the iliac arteries, and the inferior mesenteric artery.
    4. The collecting system has a characteristic appearance on intravenous urogram due to an incomplete inward rotation of the renal pelvis, which faces anterior. Q (Flower vase pattern)
  4. Investigations
    1. An IVP is the best initial radiological study to determine anatomy and relative renal function. Q
    2. CT scan or renal ultrasound is helpful to screen for the presence of stones, masses, or hydronephrosis.
    3. Further studies are performed as indicated and tailored to the clinical situation. These include: diuresis renal scan to assess renal function. Q
    4. Medical therapy: The horseshoe kidney is susceptible to medical renal disease. If present are treated as indicated.
    5. Surgical therapy: Surgical treatment is based on the disease process and standard surgical indications e.g. Ureteropelvic junction obstruction (Pyeloplasty), Kidney stones, Renal Tumors, Abdominal Aneurysmectomy (Isthmusectomy).
    6. Division of isthumus is not the treatment of choice. It is indicated only in case of surgical emergency like rupture of abdominal aortic aneurysm
Finding of IUV is Horseshoe kidney
  1. Flower vas appearance of ureter.Q
  2. Lower pole calyces lying closer to or actually overlying the spine.
  3. Pelvis is often extrarenal & large.
  1. Prognosis      
    1. The horseshoe kidney does not complicate pregnancy or delivery.
    2. Presence of the horseshoe kidney alone does not affect survival.
    3. The horseshoe kidney does have a higher propensity to become diseased. Survival is therefore dependent on the disease process that the horseshoe kidney may harbor. 

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