Congenital Anomalies and Potter's Sequence

• Congenital anomalies are birth defects.

Introduction to Congenital Anomalies

• Roughly 10% of individuals are born with notable malformations of the urinary system.
• Renal dysplasias and hypoplasias contribute to 20% of chronic kidney disease in children.
• Congenital anomalies are present at birth can be pathologically apparent at birth with multicystic renal dysplasia or show delayed phenotypic expression like APKD.
• Inherited genetic abnormalities or genetic mutations during embryogenesis, along with somatic developmental abnormalities acquired during embryogenesis or fetal development, are causes.
• Congenital anomalies account for over 50% of abdominal masses in neonates.
• They represent the most common cause of end-stage renal disease in infants and are identified in approximately 0.5% of pregnancies.

Potter's Sequence

• Potter's sequence is formerly known as Potter’s syndrome, also known as oligohydramnios sequence.
• It involves a range of abnormalities arising from severe intrauterine impairment of urine production or other factors causing oligohydramnios.
• Bilateral urinary tract obstruction, bilateral agenesis, bilateral renal aplasia, severe bilateral renal dysplasia, childhood polycystic kidney disease, or amniotic fluid leakage can cause this.
• Patients might exhibit low-set ears, a receding chin, a beak-like nose, and pulmonary hypoplasia.
• Genitalia and lower limb anomalies can also occur.
• External abnormalities result from the absence of the cushioning effect of amniotic fluid, leading to compression of the fetus by the uterine walls.
• Pulmonary hypoplasia develops due to a lack of maturational stimuli from amniotic fluid and compression of the chest wall by the uterus.

Renal Agenesis

• Renal agenesis involves the complete absence of renal tissue.
• It can manifest unilaterally or bilaterally.
• It occurs in 1 in 500 to 3200 births.
• Bilateral renal agenesis is not compatible with life without medical assistance after birth, with most infants being stillborn.
• Unilateral agenesis causes no immediate renal functional impairment, and the remaining kidney undergoes hypertrophy to maintain normal function.
• Hypertension, proteinuria, and progressive renal failure may develop later because of secondary FSGS.
• Most patients with unilateral agenesis do not develop clinically significant renal abnormalities, and the agenesis is found incidentally, like during an autopsy.
• Grossly, one or both kidneys are completely absent.
• The ureter and bladder trigone are completely absent in most patients, although less than ¼ have a vestigial distal ureter.
• With unilateral agenesis, the remaining kidney undergoes hypertrophy.
• Unilateral and bilateral renal agenesis often accompanies other congenital anomalies like internal and external genital tract malformations, imperforate anus, rectal atresia, rectourethral fistula, and a variety of CVS and neural tube defects.
• Bilateral agenesis can be accompanied by atresia or absence of the bladder and ureter.
• Severe caudal regression may manifest as absence of the distal git, external genitalia and sacrum, and fusion of vestigial lower extremities, called sirenomelia.
• Bilateral agenesis causes Potter's sequence.

Renal Hypoplasia

• Renal hypoplasia is defined as a reduction in renal mass due to insufficient genesis of normal renal tissue without histological malformation.
• It includes kidneys with 6 or fewer renal lobes, indicating too few nephrons.
• The differential diagnosis is a small kidney secondary to atrophy or scarring.
• Simple hypoplasia shows no histologic abnormalities.
• It can occur bilaterally, resulting in renal failure in early childhood, but is more commonly a unilateral defect.
• True hypoplasia is extremely rare.
• Most reported cases are acquired scarring due to vascular, infectious, or other parenchymal diseases.
• A truly hypoplastic kidney is without scars, and has a reduced number of renal lobes and pyramids.
• Oligomeganephronia, a form of renal hypoplasia, the kidney is small, and the nephrons are markedly hypertrophied due to the reduced number of nephrons.
• Simple or true hypoplasia is usually unilateral, whereas oligomeganephronia is usually bilateral.

Ectopic Kidney

• An ectopic kidney involves an abnormal kidney location, usually in the pelvis.
• This commonly results from the fetal kidney failing to migrate from the pelvis.
• Kidneys are typically normal or small in size but otherwise unremarkable.
• It can be unilateral or bilateral.
• When ureters drain into the appropriate side of the bladder, it may also be simple.
• It may be crossed; the ectopic ureter crosses the midline and drains into the bladder's contralateral side.
• Due to their abnormal position, kinking or tortuosity of the ureters may cause obstruction to urinary flow and predispose bacterial infection.

Horseshoe Kidney

• Horseshoe kidney is characterized by the fusion of the upper (10%) or lower pole (90%) of the kidneys.
• It produces a single large midline organ that is continuously crosses the midline anterior to the great vessels.
• It results from failure of the renal anlage to divide.
• Horseshoe kidney is found in 1 to 500 to 1000 autopsies and has no clinical repercussions.