Fanconi tubular syndrome is characterised by malabsorption of various electrolytes and substances commonly absorbed by the proximal tubule. Hypokalaemia, hypophosphatemia, and hyperchloremic metabolic acidosis is usually present. Also, urinalysis reveals an increased fractional excretion of glucose.

The most common physiological factors that influence renin secretion include renal perfusion pressure, renal sympathetic nerve activity, and tubular sodium chloride load.The perfusion pressure in the renal artery is the most profound parameter to influence renin secretion| when the renal perfusion pressure falls (i.e. hypovolaemia), renin secretion rises, and vice versa.

The child most likely has nephritic syndrome which is characterised by a reduced renal function, proteinuria of non-nephrotic range, haematuria, erythrocyte casts, and oedema. Polyarteritis nodosa usually occurs in middle-aged men but can also be seen in young children. It is accompanied by severe systemic manifestations such as fever, malaise, weight loss and myalgia.Renal cell carcinoma usually presents around 55 years with the classic triad of haematuria, loin pain and a unilateral mass in the flank.Polycystic kidney disease usually presents in adult life with acute loin pain and palpation of masses in the flanks.

Gitelman syndrome is a kidney disorder that causes an imbalance of charged atoms (ions) in the body, including ions of potassium, magnesium, and calcium.The signs and symptoms of Gitelman syndrome usually appear in late childhood or adolescence. Common features of this condition include painful muscle spasms (tetany), muscle weakness or cramping, dizziness, and salt craving. Also common is a tingling or prickly sensation in the skin (paraesthesia), most often affecting the face. Some individuals with Gitelman syndrome experience excessive tiredness (fatigue), low blood pressure, and a painful joint condition called chondrocalcinosis. Studies suggest that Gitelman syndrome may also increase the risk of a potentially dangerous abnormal heart rhythm called ventricular arrhythmia.

Among the options provided, the most characteristic finding that can be expected in his patient’s urine microscopy is RBC casts. Red cell casts are a characteristic feature of acute nephrotic syndrome. Other options:- Hyaline casts may be seen in normal urine, particularly after exercise. – Coarse granular casts occur in glomerular and tubular disease. – Tubular cell casts may be seen in patients with acute tubular necrosis. – The presence of 10 or more white blood cells/mm3 is abnormal and indicates an inflammatory reaction, most commonly due to infection.

Haemolytic uremic syndrome belongs to a heterogeneous group of disorders characterized by a triad of thrombocytopenia, microangiopathic haemolytic anaemia, and acute kidney injury. It is one of the most common causes of renal injury in children. The clinical findings are due to thrombotic microangiopathy, which leads to arterioles and capillary wall thickening along with endothelial swelling and detachment. The significant laboratory findings include increased white cell count, raised serum urea and creatinine, increased serum LDH, decreased platelet count, haematuria, and proteinuria.

The right testicular vein is a tributary of the inferior vena cava, while the left testicular vein drains into the left renal vein.Note:The testicular venous drainage begins in the septa and these veins together with those of the tunica vasculosa converge on the posterior border of the testis as the pampiniform plexus. The pampiniform plexus, in turn, drains to the testicular vein.

Hypospadias is an abnormality of anterior urethral and penile development. The urethral opening is located on the ventral aspect of the penis proximal to the tip of the glans penis, which, in this condition, is open. The urethral opening may be located as proximal as in the scrotum or perineum. The penis may also have associated ventral shortening and curvature, called chordee, with more proximal urethral defects.

The presenting features with the positive pregnancy test are highly suggestive of gestational diabetes mellitus.Diabetes Insipidus:It is much less common than gestational diabetes mellitus. It is characterised by the inability to concentrate urine, with marked thirst.Presenting symptoms include polydipsia (>3L daily), polyuria, nocturia, nocturnal enuresis.Physical examination may reveal features of dehydration and an enlarged bladder.Investigations include biochemical analysis for electrolytes, urine and plasma osmolality, fluid deprivation test, and cranial MRI.The main differential diagnosis is for diabetes insipidus is psychogenic polydipsia.There are three broad categories of diabetes insipidus (DI): – Central (cranial) DI: It is the most common form of diabetes insipidus.It occurs due to decreased secretion of ADH. It usually occurs due to hypothalamic disease and may show response to low-dose desmopressin.- Peripheral (nephrogenic) DI:It is characterised by the resistance of the kidney to ADH.It usually does not respond to low-dose desmopressin.- Gestational DI:It is rare and is mostly seen in teenage pregnancy.It usually presents in the third trimester and often resolves 4-6 weeks post-partum.

Nephrogenic Diabetes Insipidus is an acquired or hereditary condition that affects the water balance. It presents with polyuria and polydipsia, leading commonly to dehydration.

Allergy: A history of a prior allergic-like reaction to contrast media is associated with an up to a 5-fold increase in the likelihood of experiencing a subsequent reaction. Also, any patient with a predilection to allergic reactions may predispose them to a reaction after the administration of contrast media. Given the increased risk of severe life-threatening anaphylaxis related to the administration of contrast media in the setting of the history of atopy, the risk versus benefits should be discussed before following through with the procedure. A premedication regimen may be used to reduce the risk of anaphylaxis.Asthma: A history of asthma may be indicative of a higher likelihood of developing a contrast reaction. Cardiac status: Attention must be turned to patients with significant cardiac disease (congestive heart failure, aortic stenosis, severe cardiomyopathy, and/or pulmonary hypertension), as higher volumes and osmolality of contrast material may result in an increased risk for a contrast reaction.Renal insufficiency: Contrast nephrotoxicity is defined as the rapid deterioration of renal function after the administration of contrast media when no other aetiology can be determined from the clinical records. The major predisposing risk factors include pre-existing renal insufficiency (defined as serum creatinine level >1.5 mg/dL) and diabetes. Other risk factors include dehydration, cardiovascular disease, the use of diuretics, advanced age (>70 years old), hypertension, and hyperuricemia. Obtaining multiple contrast-enhanced studies within 24 hours is also thought to increase the risk for contrast-induced nephrotoxicity. Miscellaneous: Relative contraindications to the use of high osmolality iodinated contrast media (HOCM) in patients with pheochromocytoma, sickle cell disease, and multiple myeloma have been reported. Although the administration of low osmolality or iso-osmotic contrast media may be beneficial in patients with pheochromocytoma and sickle cell disease, little evidence suggests that these agents mitigate the risks associated with multiple myeloma.

Diffuse proliferative glomerulonephritis is a term used to describe a distinct histologic form of glomerulonephritis common to various types of systemic inflammatory diseases, including autoimmune disorders (e.g., systemic lupus erythematosus [SLE]), vasculitis syndromes (e.g., granulomatosis with polyangiitis), and infectious processes. In DPGN, more than 50% of the glomeruli (diffuse) show an increase in mesangial, epithelial, endothelial (proliferative), and inflammatory cells (i.e., glomerulonephritis).

Tuberous sclerosis presents with the growth of numerous noncancerous (benign) tumours in many parts of the body. They may appear in the brain, kidneys, skin or various other organs.

Polyuria is defined as a total increase in the urine output or > 2L/m2 of daily urine produced in children. Polyuria can be a symptom of a vast number of medical conditions. The commonest and most important disease having polyuria as the main symptom is diabetes mellitus. Nephrogenic and central diabetes insipidus also results in polyuria along with polydipsia. Other conditions that lead to an increase in the urine output are renal failure, acute tubular necrosis, and exposure to high altitude. Hyperkalaemia does not result in polyuria| rather hypokalaemia can be an associated finding with polyuria in the case of diuretic abuse.

Alport syndrome is a genetic condition characterized by kidney disease, hearing loss, and eye abnormalities. Alport syndrome can have different inheritance patterns. About 80 percent of cases are caused by mutations in type IV collagen genes (COL4A5) and are inherited in an X-linked autosomal recessive pattern, although other inheritance patterns exist. Alport syndrome has autosomal dominant inheritance in about 5 percent of cases.

People with Alport syndrome experience progressive loss of kidney function. Almost all affected individuals have blood in their urine (haematuria), which indicates abnormal functioning of the kidneys. Many people with Alport syndrome also develop high levels of protein in their urine (proteinuria). The kidneys become less able to function as this condition progresses, resulting in end-stage renal disease (ESRD).

People with Alport syndrome frequently develop sensorineural hearing loss, which is caused by abnormalities of the inner ear, during late childhood or early adolescence. Affected individuals may also have misshapen lenses in the eyes (anterior lenticonus) and abnormal coloration of the light-sensitive tissue at the back of the eye (retina). These eye abnormalities seldom lead to vision loss.

Significant hearing loss, eye abnormalities, and progressive kidney disease are more common in males with Alport syndrome than in affected females.

Haemolytic-uremic syndrome (HUS) is a clinical syndrome characterized by progressive renal failure that is associated with microangiopathic (nonimmune, Coombs-negative) haemolytic anaemia and thrombocytopenia. HUS is the most common cause of acute kidney injury in children. It predominantly occurs in infants and children after prodromal diarrhoea. In summer epidemics, the disease may be related to infectious causes.Bacterial infections may include the following:S dysenteriaeE ColiSalmonella typhiCampylobacter jejuniYersinia pseudotuberculosisNeisseria meningitidisS pneumoniaLegionella pneumophilaMycoplasma speciesRickettsial infections may include Rocky Mountain spotted fever and microtatobiotesViral infections may include the following:Human immunodeficiency virus (HIV)CoxsackievirusEchovirusInfluenza virusEpstein-Barr virusHerpes simplex virusFungal infections can include Aspergillus fumigatus.Vaccinations may include the following:Influenza triple-antigen vaccineTyphoid-paratyphoid A and B (TAB) vaccinePolio vaccinePregnancy-associated HUS occasionally develops as a complication of preeclampsia. Patients may progress to full-blown haemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Postpartum HUS usually occurs within 3 months of delivery. The prognosis is poor, with a 50-60% mortality rate, and residual renal dysfunction and hypertension occur in most patients.

Membranoproliferative glomerulonephritis primarily affects children and young adults, with patients presenting with nephrotic or nephritic syndrome or with asymptomatic renal disease. There are 3 types defined by pathologic features. All three types are associated with hypocomplementemia, but they manifest somewhat different mechanisms of complement activation. This type of glomerulonephritis often progresses slowly to end-stage renal disease, and it tends to recur after renal transplantation, especially type II.

The most probable cause for the child’s presenting symptoms and the findings in ultrasound would be the presence of an abnormal posterior urethral valve. A posterior urethral valve is a developmental anomaly that usually affects male infants (incidence 1 in 8000) leading to obstructive uropathy. Diagnostic features include bladder wall hypertrophy, hydronephrosis and bladder diverticula.Note:Posterior urethral valves are the most common cause of infra-vesical outflow obstruction in males. They can be diagnosed on antenatal ultrasonography. Due to the necessity of the fetal bladder to develop high emptying pressures in utero secondary to this anomaly, the child may develop renal parenchymal damage. This leads to renal impairment noted in 70% of boys at the time of presentation. Management:The immediate treatment would be to place a bladder catheter to relieve the acutely retained urine. The definitive treatment of choice would be an endoscopic valvotomy with a cystoscopic and renal follow up.

The most probable diagnosis for this patient would be torsion of a hydatid cyst of the testis.Note:The differential diagnoses in acute testicular pain/swelling are listed in the possible answers. Testicular torsion typically affects adolescent males and presents with acute painful swelling and a horizontally lying testicle. Other options:- Epididymo-orchitis is diagnosed during surgery when a thickened erythematous epididymis is noted. Ectopic ureteric insertion into the vas must be excluded by ultrasound scan on an out-patient basis. The hydatid cyst or cyst of Morgagni represents the remnants of the Mullerian structure. In the pre-pubertal child, a surge in hormones can stimulate growth and chance of torsion. It is diagnosed by surgical exploration or by a blue dot sign. Idiopathic scrotal oedema tends to be within the scrotum itself, and the testis can be examined in the groin to exclude pain in the testis. All acute scrotal pain must be explored to exclude testicular torsion unless a surgical registrar is convinced of a torted hydatid cyst.- An 8-year-old is more likely to present with a torted hydatid cyst. The blue dot sign is diagnostic and can negate the need for surgical exploration. The age of the child also makes epididymo-orchitis less likely.- Idiopathic scrotal oedema presents with an erythematous and thickened scrotum. This can cross the midline and involve the whole scrotum.- Finally, an inguinal hernia would present with a mass in the groin extending to the scrotum that you cannot get above.

Distal renal tubular acidosis (dRTA) is characterised by a decreased hydrogen ion excretion from the alpha intercalated cells of the collecting duct of the distal nephron. The resultant acidosis causes calcium and phosphates to be released from bones to buffer the acidosis causing hypercalciuria. This precipitates calcium compounds in the kidney, predisposing it to renal stone formation. On the other hand, proximal renal tubular acidosis is characterised by an impairment in bicarbonate resorption. Both types lead to metabolic acidosis and electrolyte imbalances including potassium depletion. Children often present with failure to thrive. One way to differentiate between the two conditions is with an acid challenge test. In proximal RTA (type 2) administering an ammonium chloride load will decrease the urinary pH whereas in distal disease (type 1), the urine pH will not decrease below 5.3.

Renal scaring resulting from urinary tract infections can best be determined using Dimercaptosuccinic acid (DMSA) scintigraphy. The scan utilises technetium-99 mixed with the DMSA which is injected into the bloodstream. The radiological dye is taken up by the kidney where it binds to the proximal convoluted tubules. It therefore detects the size, shape and position of the kidney and any scars but is not as useful in assessing dynamic renal excretion. Ultrasound scans are better suited to assess hydronephrosis and dilated ureters. MAG3 scans and MCUG are able to determine the function of kidneys and detect obstructions such as posterior urethral valves and reflux.

Among the given options, the most likely cause for the patient’s presenting symptoms is acute interstitial nephritis secondary to anti-tubercular therapy (ATT)Drug-induced acute interstitial nephritis can occur following treatment with beta-lactams, sulphonamides, rifampicin, ethambutol, and erythromycin. They can cause an acute allergic reaction with the infiltration of immune cells.Acute interstitial nephritis is said to be the most common renal complication in patients undergoing anti-TB treatment. Rifampicin is the most implicated drug, although ethambutol can also be a cause. The pathogenesis involves an immune-complex mediated acute allergic response, which leads to their deposition on renal vessels, the glomerular endothelium, and the interstitial area. Other options:Isoniazid does not affect the kidneys. Pulmonary-renal syndrome is a feature of Goodpasture’s syndrome. It is characterized by renal failure and lung haemorrhage. Severe cardiac or renal failure ensues and is complicated by pulmonary oedema, systemic lupus erythematosus, Henoch-Schönlein purpura, and cryoglobulinemia.

Constipation is often associated with nocturnal enuresis in children. The palpable mass is the impacted stool. The decreased appetite is common in those with constipation.

Fanconi syndrome is a rare disorder characterized by defective proximal renal tubular reabsorption, which leads to excessive excretion of potassium, phosphate, uric acid, bicarbonates, glucose, and certain amino acids in the urine. Loss of potassium in the urine leads to hypokalaemia, while the loss of phosphate may lead to hypophosphatemic rickets. The overall impact is the failure to thrive and growth retardation.

The child has nephrotic syndrome which is most commonly caused by minimal change nephropathy in this age group. The condition presents with fusion of foot processes of the glomerular epithelial cells under the microscope.

Proteinuria refers to an increased amount of protein excretion in urine, which should be greater than 100mg/m2 per day on a single spot urine collection. The limit is even more relaxed for infants and neonates. Proteinuria is a prominent manifestation of cystinosis, acute tubular necrosis, Fanconi syndrome, and celiac disease. Landau-Kleffner syndrome is a rare childhood convulsive disorder, associated with acquired aphasia and auditory verbal agnosia.

The most common manifestation of Wilms tumour is an asymptomatic abdominal mass| an abdominal mass occurs in 80% of children at presentation. Abdominal pain or haematuria occurs in 25%. Urinary tract infection and varicocele are less common findings than these. Hypertension, gross haematuria, and fever are observed in 5-30% of patients. A few patients with haemorrhage into their tumour may present with hypotension, anaemia, and fever. Rarely, patients with advanced disease may present with respiratory symptoms related to lung metastases.

Based on the presented clinical scenario, the most probable diagnosis for the patient would be testicular torsion.Rationale:The gubernaculum is the structure responsible for aiding the descent of the testicles from the abdomen into the scrotum. The processus vaginalis precedes the descent of the testes and then undergoes closure. Abnormalities such as the persistence of a patent processus vaginalis, known as bell clapper deformity, predispose to testicular torsion.Other options:- Varicocele: Nutcracker syndrome occurs where the left renal vein becomes compressed in between the superior mesenteric artery and the aorta. Since the left gonadal vein drains into the left renal vein, this results in a varicocele. – Epididymitis and mumps orchitis are differentials for acute testicular pain but are not due to a defect in the processus vaginalis. – An incarcerated inguinal hernia presents mainly with signs of bowel obstruction which are not mentioned in the clinical scenario.The descent of testes:- Until the end of foetal life, the testicles are located within the abdominal cavity. – They are initially located on the posterior abdominal wall on a level with the upper lumbar vertebrae (L2). – Attached to the inferior aspect of the testis is the gubernaculum testis which extends caudally to the inguinal region, through the canal and down to the superficial skin. – It is interesting to note that both the testis and the gubernaculum are extra-peritoneal.- As the foetus grows, the gubernaculum becomes progressively shorter. It carries the peritoneum of the anterior abdominal wall (the processus vaginalis). As the processus vaginalis descends the testis is guided by the gubernaculum down the posterior abdominal wall and the back of the processus vaginalis into the scrotum.- By the third month of foetal life the testes are located in the iliac fossae, by the seventh they lie at the level of the deep inguinal ring.Usually, the processus vaginalis closes after birth but may persist predisposing to indirect hernias. On the other hand, a partial closure may result in the development of cysts on the cord.

Coverings of the spermatic cord:Spermatic cord is covered by three concentric layers of fasciae, derived from the layers the of anterior abdominal wall. Developmentally, each covering is acquired as the processus vaginalis descends into the scrotum through the layers of the abdominal wall. The layers are:External spermatic fascia: It is derived from the external oblique muscle. It attaches to the margins of superficial inguinal ring.Cremasteric fascia: It is derived from the internal oblique muscle. It covers the cremaster muscle.Internal spermatic fascia: It is derived from the fascia transversalis (fascia covering the transversus abdominis muscle). It is attached to the margins of the deep inguinal ring.

Hyperkalaemia is not to evaluate or detect AKI but rather the result of it. If one of the rest of the options is present, then AKI would be suspected.