Hydronephrosis (Study Outline) 1. Background Definition: Dilation of the renal pelvis and calyces due to obstruction of urine flow, leading to increased intrarenal pressure and possible renal damage. Pathophysiology: Obstruction → urine backs up into kidney → ↑ hydrostatic pressure → tubular injury and decreased GFR. Chronic obstruction leads to cortical thinning, interstitial fibrosis, and potential permanent renal loss. Etiologies (high-yield): Postrenal obstruction: stones, BPH, ureteral strictures, tumors. Congenital causes: ureteropelvic junction (UPJ) obstruction, vesicoureteral reflux. Pregnancy: physiologic dilation from progesterone and extrinsic compression. Neurogenic bladder and functional obstruction. 2. History Flank pain: dull if chronic; acute severe colicky pain suggests stone. Lower urinary symptoms: hesitancy, weak stream, incomplete emptying (BPH/outlet obstruction). Decreased urine output or intermittent anuria (complete obstruction). Recurrent UTIs or pyelonephritis. Hematuria: often with stones. Systemic symptoms: fever or chills if infection present (obstructive pyelonephritis = high-yield emergency concept). 3. Exam Findings Flank or costovertebral angle tenderness. Palpable bladder in lower tract obstruction. Prostate enlargement on DRE (conceptual). Signs of infection: fever, tachycardia in obstructive pyelonephritis. Chronic obstruction: may have minimal findings despite significant hydronephrosis. 4. Making the Diagnosis Labs: May show elevated BUN/Cr if bilateral obstruction or solitary kidney. UA: hematuria (stones), pyuria/bacteriuria (infection), otherwise bland. Imaging (high-yield): Renal ultrasound = first-line Shows dilation of renal pelvis/calyces; assesses obstruction severity. CT abdomen/pelvis (non-contrast): best for stones and acute obstruction. MRI/functional studies (MAG3 renal scan): evaluate suspected chronic obstruction and differential renal function. Key concept: Must identify cause of obstruction for complete diagnosis. Gold Standard: Imaging-confirmed collecting system dilation consistent with obstruction. 5. Management (Exam Concepts) General principle: Relieve obstruction to prevent irreversible renal damage. Common causes and conceptual interventions: Stones: determine need for urologic intervention based on size/location (exam concept only). BPH/outlet obstruction: bladder decompression concepts. Ureteral obstruction from mass/stricture: consider upper tract decompression conceptually. Infection + obstruction (high-yield emergency): Obstructive pyelonephritis requires urgent decompression conceptually (no procedural details). Supportive concepts: Monitor renal function and electrolytes. Avoid nephrotoxins; adjust medications for impaired GFR. Address underlying chronic cause (e.g., neurogenic bladder strategies). Referral: urology for intervention; nephrology for compromised renal function or recurrent obstruction. QUESTION A 70-year-old man presents to the emergency department with fever, chills, and left-sided flank pain for the past day. He reports difficulty urinating and a feeling of incomplete bladder emptying for the past several months. His medical history includes benign prostatic hyperplasia (BPH). On exam, temperature is 38.9°C (102°F), heart rate is 112/min, and blood pressure is 130/78 mmHg. He has left CVA tenderness and a distended bladder is palpable. Laboratory findings: WBC count: 16,500/μL Creatinine: 2.1 mg/dL (baseline 1.1) Urinalysis: pyuria, bacteriuria, no casts Renal ultrasound: moderate left-sided hydronephrosis and bladder distention Which of the following is the most appropriate next step in management? A) Start empiric antibiotics and monitor closelyB) Begin intravenous fluids and schedule CT scanC) Insert a urinary catheter to relieve obstructionD) Order MRI of the kidneys to evaluate functional loss

Hyponatremia (Study Outline) 1. Background Definition: Serum sodium

Focal Segmental Glomerulosclerosis (FSGS) (Study Outline) 1. Background Definition: A nephrotic syndrome caused by segmental sclerosis of some (focal) glomeruli, due to podocyte injury. Pathophysiology: Podocyte damage → leakage of protein → progressive scarring of glomeruli. Can progress to CKD/ESRD if untreated. Epidemiology: One of the most common causes of nephrotic syndrome in adults, especially in African American patients. Etiologic categories: Primary (idiopathic): sudden heavy proteinuria. Secondary: HIV (HIV-associated nephropathy), obesity, heroin use, sickle cell disease, reduced nephron mass, reflux nephropathy. Key concept: More likely than Minimal Change Disease to progress to chronic kidney disease. 2. History Edema: gradual onset, lower extremities ± periorbital. Proteinuria: often heavy (>3.5 g/day), leading to foamy urine. Hypertension: more common than in minimal change disease. Clues for secondary forms: IV drug use (heroin), HIV risk factors, obesity, long-standing HTN, solitary kidney. Symptoms of CKD if progression: fatigue, anorexia, nocturia. 3. Exam Findings Edema: pitting, may progress to anasarca. Blood pressure: frequently elevated. Signs of underlying etiology: Skin lesions or opportunistic infections (HIV). Obesity or signs of metabolic syndrome. Possible findings of hyperlipidemia: xanthelasma (less common). 4. Making the Diagnosis Urinalysis: Nephrotic-range proteinuria. Fatty casts, oval fat bodies. Hematuria may occur but is not dominant. Blood tests: hypoalbuminemia, hyperlipidemia; varying degrees of renal insufficiency. Serologic workup: rule out secondary causes (HIV testing, ANA, complement levels, hepatitis panel). Renal ultrasound: usually normal-sized kidneys. Renal biopsy (Gold Standard): Segmental sclerosis of some glomeruli on light microscopy. Foot process effacement on EM (similar to minimal change, but with sclerosis). IF often nonspecific or segmental IgM/C3 trapping. 5. Management (Exam Concepts) General nephrotic syndrome principles: Sodium restriction concepts for edema. Monitor renal function and electrolytes; avoid nephrotoxins; adjust renally cleared medications. Proteinuria reduction (high-yield): RAAS modulation principles to reduce intraglomerular pressure. Immunosuppression concepts: Often used in primary FSGS; variable response (unlike MCD). Treat underlying cause: HIV management principles for HIVAN. Weight reduction in obesity-related FSGS. Hyperlipidemia management: conceptual lipid-lowering. CKD risk monitoring: FSGS has a higher likelihood of progression to ESRD; monitor for declining GFR. Referral: any suspected FSGS or progressive proteinuria. QUESTION A 35-year-old African American man presents with gradual swelling in his legs and foamy urine for several weeks. He reports fatigue and mild shortness of breath. He has a history of intravenous heroin use. Vital signs reveal a blood pressure of 148/90 mmHg. Physical exam shows bilateral pitting edema up to the knees. Laboratory studies show: Serum albumin: 2.4 g/dL Creatinine: 1.7 mg/dL (baseline unknown) Total cholesterol: 285 mg/dL Urinalysis: 4+ protein, few RBCs, fatty casts 24-hour urine protein: 6.5 g HIV test: negative Which of the following best explains the underlying pathophysiology of this patient’s condition? A) T-cell cytokine-mediated podocyte injuryB) Immune complex deposition in the mesangiumC) Segmental glomerular scarring due to podocyte lossD) Anti-GBM antibody attack on basement membrane

Nephrotic Syndrome (Study Outline) 1. Background Definition: A glomerular disorder characterized by heavy proteinuria (>3.5 g/day), hypoalbuminemia, edema, hyperlipidemia, and lipiduria. Pathophysiology: Injury to the glomerular filtration barrier (podocytes) → massive loss of protein → ↓ plasma oncotic pressure → edema and hepatic upregulation of lipoprotein synthesis. Common causes (high-yield): Primary: Minimal change disease (most common in children). Focal segmental glomerulosclerosis (FSGS). Membranous nephropathy (most common in adults). Secondary: Diabetes mellitus (leading cause). Amyloidosis. SLE (can cause nephritic or nephrotic). Infections (HIV, hepatitis), medications, malignancy. 2. History Edema—generalized, often periorbital in AM and dependent in PM. Foamy urine (due to proteinuria). Fatigue, weight gain from fluid retention. History clues for secondary causes: Longstanding diabetes, IV drug use, HIV risk, hepatitis exposure, autoimmune symptoms, malignancy. Thrombotic history: nephrotic state increases risk for DVT/PE. 3. Exam Findings Edema: pitting, generalized (anasarca in severe cases). Ascites, pleural effusions in advanced disease. Labs may manifest clinically: xanthelasma (hyperlipidemia). Possible hypertension (less pronounced than nephritic syndrome). Signs of underlying disease: diabetic retinopathy, purpura (amyloidosis rare), rash (SLE). 4. Making the Diagnosis Urinalysis: Massive proteinuria (>3.5 g/day). Oval fat bodies (“Maltese cross” under polarized light). Lipiduria, fatty casts. Blood tests: Hypoalbuminemia, hyperlipidemia (↑ LDL, ↑ triglycerides). May have normal or mildly low GFR initially. Serologic testing based on suspected etiology: Autoimmune panel (ANA, anti-dsDNA), hepatitis serologies, HIV testing. Renal ultrasound: typically normal-sized kidneys. Renal biopsy: Often required to determine etiology (minimal change vs. FSGS vs. membranous). Gold Standard: Renal biopsy demonstrating characteristic podocyte/glomerular changes consistent with specific nephrotic pathology. 5. Management (Exam Concepts) General principles: Control edema (concept-level: sodium restriction). Adjust medications based on GFR. Avoid nephrotoxins. Proteinuria reduction (high-yield exam concept): RAAS modulation principles for reducing intraglomerular pressure and protein loss. Hyperlipidemia management: conceptual treatment of elevated LDL/TG in nephrotic states. Thrombosis risk: nephrotic syndrome increases clot risk—recognize risk factors conceptually. Cause-directed (exam-level concepts): Minimal change disease: immunosuppression principles. FSGS: BP control, immunosuppression concepts. Membranous nephropathy: immunologic evaluation and immunosuppression principles. Diabetic nephropathy: optimize glucose/BP. Indications for referral: heavy proteinuria, unclear cause, or progression toward CKD. QUESTION A 36-year-old man presents with progressive swelling in his legs and face over the past two weeks. He also reports frothy urine and a recent 6-pound weight gain. He denies hematuria, joint pain, or rash. Medical history is significant for intravenous drug use. On exam, his blood pressure is 132/82 mmHg, and he has periorbital edema, pitting edema to the knees, and mild ascites. Laboratory studies: Urinalysis: 4+ protein, no hematuria, oval fat bodies 24-hour urine protein: 7.2 g Serum albumin: 2.1 g/dL (3.5–5.0) Serum creatinine: 1.1 mg/dL Total cholesterol: 294 mg/dL HIV test: positive Which of the following is the most likely diagnosis? A) Focal segmental glomerulosclerosisB) Membranous nephropathyC) Minimal change diseaseD) Diabetic nephropathy

Chronic Kidney Disease (CKD) (Study Outline) 1. Background Definition: Persistent kidney dysfunction ≥3 months with structural or functional abnormalities, often with decreased GFR. Epidemiology: Common in diabetes and hypertension; major contributor to cardiovascular morbidity. Pathophysiology: Nephron loss → compensatory hyperfiltration → progressive sclerosis. Declining GFR → impaired fluid, electrolyte, acid-base, endocrine functions. Common causes (high-yield): Diabetes mellitus (#1) Hypertension (#2) Glomerulonephritis, polycystic kidney disease, chronic obstruction, recurrent pyelonephritis. Staging: Based on GFR and albuminuria categories. 2. History Often asymptomatic in early stages. General symptoms: fatigue, weakness, anorexia, pruritus. Fluid/electrolyte symptoms: edema, dyspnea, nocturia. Uremic findings (late): nausea, metallic taste, cognitive changes. Comorbid condition clues: longstanding diabetes, poorly controlled hypertension. Medication history relevant for nephrotoxins. 3. Exam Findings Vital signs: hypertension common. Volume status: peripheral edema, pulmonary crackles (volume overload). Skin: uremic frost (late, rare), hyperpigmentation. Neuro: asterixis in advanced uremia. Cardiac: pericardial rub (uremic pericarditis). Findings of underlying disease: e.g., diabetic neuropathy, retinopathy. 4. Making the Diagnosis Key labs: Persistent ↓ GFR (

Diabetic Nephropathy (Study Outline) 1. Background Definition: A chronic, progressive kidney disease caused by long-term diabetes mellitus, leading to albuminuria, declining GFR, and eventual CKD/ESRD. Epidemiology: Most common cause of ESRD in the U.S. Occurs in both type 1 and type 2 diabetes. Pathophysiology: Chronic hyperglycemia → nonenzymatic glycosylation → basement membrane thickening + mesangial expansion. Glomerular hyperfiltration early → podocyte loss → sclerosis (Kimmelstiel–Wilson nodules). Progression (typical): Hyperfiltration Microalbuminuria Macroalbuminuria Declining GFR ESRD 2. History Often asymptomatic early. Classic early clue: new or worsening microalbuminuria. Later symptoms relate to CKD: fatigue, edema, nocturia. Longstanding diabetes (poor control, long duration). Coexisting diabetic complications: retinopathy (high-yield), neuropathy. Cardiovascular risk factors: HTN, dyslipidemia, obesity. 3. Exam Findings Blood pressure: usually elevated. Edema: peripheral or periorbital as protein loss increases. Diabetic complications: Retinopathy (high-yield correlation with nephropathy). Peripheral neuropathy. Signs of advanced CKD: pallor (anemia), asterixis, crackles (volume overload). 4. Making the Diagnosis Urine testing: Urine albumin-to-creatinine ratio (ACR): Microalbuminuria = 30–300 mg/day equivalent. Macroalbuminuria >300 mg/day. Persistent albuminuria on ≥2 tests over 3 months. Urinalysis: Proteinuria; may progress to nephrotic-range. No hematuria typically (unless another renal disease). Renal function: Gradual decline in GFR; increasing BUN/Cr. Serology: usually normal (normal complements, no immune markers). Imaging: renal ultrasound normal or enlarged early; may be small later. Renal biopsy: Not routinely required unless atypical. Would show Kimmelstiel–Wilson nodules (nodular glomerulosclerosis). Gold Standard: Persistent albuminuria + diabetic history + absence of alternative cause, confirmed clinically. 5. Management (Exam Concepts) Glycemic control: Tight glucose management slows progression (exam concept; no regimen details). BP management: RAAS modulation principles reduce intraglomerular pressure and proteinuria (high-yield). Proteinuria reduction: Central to slowing disease progression. Lifestyle concepts: Sodium restriction for edema/BP; weight management. CKD complication monitoring: Hyperkalemia, acidosis, anemia, bone-mineral disease, hyperphosphatemia. Avoid nephrotoxins and adjust doses of renally cleared medications. Cardiovascular risk reduction: Diabetes + nephropathy markedly increases CV mortality. Dialysis indications: AEIOU concept if ESRD develops. Referral: albuminuria progression, rapid GFR decline, uncertainty in diagnosis, or need for renal replacement planning. QUESTION A 62-year-old woman with a 20-year history of poorly controlled type 2 diabetes presents for routine follow-up. She reports increased lower extremity swelling and fatigue. Vitals reveal a blood pressure of 152/92 mmHg. Fundoscopic exam shows background diabetic retinopathy. Physical exam reveals bilateral pitting edema to the mid-shin. Laboratory findings include: Serum creatinine: 1.8 mg/dL (baseline 1.0 mg/dL one year ago) Urine albumin-to-creatinine ratio: 820 mg/g Serum potassium: 4.9 mEq/L Hemoglobin A1c: 9.1% ANA, C3/C4: normal Which of the following is the most appropriate next step in management to slow the progression of her renal disease? A) Begin sodium bicarbonate therapyB) Initiate an ACE inhibitorC) Schedule a renal biopsyD) Start high-dose corticosteroids

Hyperkalemia (Study Outline) 1. Background Definition: Serum potassium >5.0 mEq/L (lab-dependent). Pathophysiology: Results from impaired renal excretion, cellular shifts, or excess intake (rare alone). High extracellular K⁺ decreases resting membrane potential → cardiac conduction abnormalities (high-yield). Major causes (high-yield): Decreased excretion: Acute or chronic kidney disease. Hypoaldosteronism (Addison disease, adrenal insufficiency). Medications affecting RAAS: ACE-I/ARBs, potassium-sparing diuretics, NSAIDs. Transcellular shifts: Metabolic acidosis. Insulin deficiency (DKA). Tissue breakdown (rhabdomyolysis, tumor lysis, hemolysis). Pseudohyperkalemia: hemolysis of blood sample (important exam clue). 2. History Often asymptomatic early. Muscle symptoms: weakness, flaccid paralysis, paresthesias. Cardiac symptoms: palpitations, lightheadedness, syncope (if arrhythmias). Etiology clues: Kidney dysfunction (oliguria, history of CKD). Recent medication changes (RAAS drugs). Acidosis, DKA symptoms (polyuria, abdominal pain). Trauma/exertion (rhabdomyolysis). Cancer therapy (tumor lysis). 3. Exam Findings Muscle weakness or decreased reflexes. Bradycardia or irregular pulse (arrhythmias). Signs of underlying cause: Volume depletion (DKA). Muscle tenderness (rhabdo). Hypotension or shock (renal failure, adrenal insufficiency). ECG findings (very high-yield): Peaked T waves (early). Widened QRS, prolonged PR. Sine-wave pattern (pre-arrest). 4. Making the Diagnosis Serum potassium: elevated; confirm if pseudohyperkalemia suspected. Renal function tests: ↑ BUN/Cr in AKI/CKD. Arterial/venous chemistry: metabolic acidosis clues. Additional labs based on cause: CK (rhabdomyolysis). Glucose/ketones (DKA). Complete blood count (hemolysis). ECG: key for assessing severity. Gold Standard: Confirmatory serum potassium measurement with clinical correlation. 5. Management (Exam Concepts) (No real-time treatment or dosing — exam concepts only.) Immediate priorities (concept-based): Stabilize cardiac membrane (high-yield concept). Shift potassium intracellularly (concept). Enhance potassium elimination (concept). Conceptual approaches: Cardiac membrane stabilization: Calcium-based concept (no dosing). Shift K⁺ into cells: Insulin/glucose concept, β-agonist concept. Address acidosis conceptually (e.g., correct DKA). Enhance elimination: Renal excretion principles; GI binding/removal concepts. Dialysis principles for severe/refractory cases (especially CKD/ESRD). Avoid/stop contributors: RAAS drugs, potassium supplements, potassium-sparing diuretics (concept-level). Monitor: serial K⁺ levels, ECG, renal function. Indications for dialysis: severe or refractory hyperkalemia, ECG changes not improving, or concurrent severe AKI/ESRD. QUESTION A 67-year-old man presents to the emergency department with progressive muscle weakness and lightheadedness. He has a history of hypertension, chronic kidney disease stage 4, and heart failure with reduced ejection fraction. His medications include lisinopril, spironolactone, and furosemide. He denies chest pain or recent trauma. Vital signs are: blood pressure 108/67 mmHg, heart rate 52/min, respiratory rate 18/min, and oxygen saturation 97% on room air. On exam, he has decreased deep tendon reflexes and mild flaccid weakness in all extremities. ECG shows tall, peaked T waves and a widened QRS complex. Serum chemistry reveals: Potassium: 7.3 mEq/L (reference: 3.5–5.0) BUN: 48 mg/dL (reference: 7–20) Creatinine: 3.1 mg/dL (baseline: 2.5) Which of the following is the most appropriate next step in management? A) Administer intravenous calcium gluconateB) Administer sodium polystyrene sulfonateC) Initiate hemodialysisD) Administer intravenous insulin with glucose

Membranous Nephropathy (Membranous Glomerulopathy) (Study Outline) 1. Background Definition: A nephrotic syndrome characterized by immune complex deposition along the glomerular basement membrane (GBM) leading to GBM thickening. Epidemiology: Most common cause of nephrotic syndrome in non-diabetic adults. Pathophysiology: Immune complex deposition → complement activation (MAC-mediated podocyte injury) → proteinuria. Etiologies: Primary (idiopathic): associated with anti–PLA2R antibodies (high-yield). Secondary: Infections: hepatitis B/C, syphilis. Autoimmune: SLE. Malignancies (solid tumors). Medications: NSAIDs, gold, penicillamine. Course: May remit spontaneously; may progress to CKD/ESRD. 2. History Edema: insidious onset; peripheral ± periorbital. Foamy urine from heavy proteinuria. Possible systemic symptoms depending on secondary causes: Arthralgias, rash (SLE). Weight loss/night sweats (malignancy). Chronic hepatitis symptoms. Thromboembolism risk: elevated; renal vein thrombosis is classic high-yield association. 3. Exam Findings Edema: pitting, may be generalized. Possible hypertension (less pronounced early). Signs of secondary disease: Hepatomegaly/jaundice (hepatitis). Malar rash or alopecia (SLE). Lymphadenopathy or cachexia (malignancy). Pleural effusions/ascites in advanced nephrotic states. 4. Making the Diagnosis Urinalysis: Nephrotic-range proteinuria (>3.5 g/day). Lipiduria with fatty casts, oval fat bodies. Blood tests: Hypoalbuminemia, hyperlipidemia. Consider anti-PLA2R antibody testing in suspected primary disease. Serologic tests for secondary causes: ANA, hepatitis B/C serologies, syphilis testing, age-appropriate malignancy screening. Imaging: usually normal kidney size. Renal biopsy (Gold Standard): Diffuse GBM thickening on light microscopy. “Spike and dome” appearance on silver stain (high-yield). Granular IgG/C3 deposits on immunofluorescence. Key distinction: Minimal change disease has normal light microscopy; membranous has GBM thickening. 5. Management (Exam Concepts) General nephrotic syndrome principles: Conceptual sodium restriction; monitor fluid status and renal function. Avoid nephrotoxins and adjust renally cleared medications. Proteinuria reduction: RAAS modulation principles to reduce intraglomerular pressure (high-yield exam concept). Immunosuppression concepts: Indicated in persistent or severe proteinuria or declining GFR (no regimens). Secondary cause management: Treat underlying hepatitis, autoimmune disease, or malignancy at exam-concept level. Hyperlipidemia management: conceptual lipid-lowering. Thrombosis risk: recognize high risk for renal vein thrombosis in nephrotic patients. Follow-up: monitor for spontaneous remission vs. progression toward CKD. Referral: essential for biopsy interpretation, immunologic workup, and specialized management. QUESTION A 58-year-old man presents with increasing leg swelling and frothy urine for the past month. He denies fever, rash, joint pain, or recent travel. Medical history includes osteoarthritis, for which he takes ibuprofen regularly. Physical exam reveals bilateral pitting edema up to the mid-shin. Blood pressure is 138/86 mmHg. Laboratory findings: Serum albumin: 2.3 g/dL Total cholesterol: 312 mg/dL Urinalysis: 4+ protein, fatty casts, no hematuria 24-hour urine protein: 7.1 g Hepatitis B/C serologies: negative ANA: negative Serum creatinine: 1.1 mg/dL Renal biopsy shows diffuse glomerular basement membrane thickening with granular IgG and C3 deposits on immunofluorescence and a “spike and dome” appearance on silver stain. Which of the following best explains this patient’s pathophysiology? A) Immune complex deposition causing subepithelial podocyte injuryB) T-cell cytokine–mediated podocyte effacementC) Autoantibody-mediated attack on mesangial antigensD) C3 nephritic factor–mediated dense deposit formation

Hypokalemia (Study Outline) 1. Background Definition: Serum potassium

Horseshoe Kidney (Study Outline) 1. Background Definition: A congenital renal fusion anomaly where the inferior poles of both kidneys fuse, forming a U- or horseshoe-shaped structure. Epidemiology: Most common renal fusion abnormality. More common in males; often discovered incidentally. Pathophysiology: Fusion prevents normal ascent of kidneys → trapped under the inferior mesenteric artery (IMA). Altered renal position and rotation predispose to obstruction, reflux, and stones. Associated conditions: Turner syndrome, trisomy 18/21, neural tube defects. Higher risk of Wilms tumor (pediatric association). 2. History Many patients asymptomatic. Flank or abdominal pain from obstruction or hydronephrosis. Recurrent UTIs or pyelonephritis. Nephrolithiasis symptoms: colicky pain, hematuria. Voiding dysfunction in some pediatric presentations. 3. Exam Findings Frequently normal exam. Abdominal mass may be palpable in thin patients. CVA tenderness if infected or obstructed. Hypertension may occur in chronic obstruction/hydronephrosis. Associated congenital anomalies may have external manifestations (e.g., Turner syndrome features). 4. Making the Diagnosis Urinalysis: may show hematuria or pyuria depending on stones/UTI. Labs: renal function usually normal unless obstruction. Imaging (high-yield): Renal ultrasound: first-line; shows fused lower poles and abnormal renal position. CT or MRI: clearly shows renal fusion, isthmus, and associated abnormalities. VOIDING cystourethrogram (VCUG): used if vesicoureteral reflux suspected. Complications to assess: hydronephrosis, stones, obstruction. Gold Standard: Cross-sectional imaging (CT/MRI) demonstrating fusion of the renal poles and malrotated kidneys. 5. Management (Exam Concepts) General principles: Asymptomatic patients often require no intervention. Monitor renal function and watch for complications. Management of complications (conceptual): Hydronephrosis/obstruction: evaluate for relief of obstruction. Nephrolithiasis: manage stones via general exam concepts (evaluation, prevention, intervention as indicated). UTIs: recognize predisposition and manage infections at conceptual level. Vesicoureteral reflux: evaluate in pediatric recurrent UTIs. Surgical considerations: Usually not required unless symptomatic obstruction or recurrent stones. Referral: nephrology/urology for recurrent infections, obstruction, or impaired renal function. QUESTION A 9-year-old girl is brought to the pediatrician for evaluation of recurrent urinary tract infections. She has had three documented UTIs in the past year, all with similar symptoms of dysuria and low-grade fever. Her past medical history includes learning difficulties and a cardiac murmur noted at birth. Physical exam is unremarkable except for mild suprapubic tenderness. Her blood pressure is 112/72 mmHg. Urinalysis shows pyuria and bacteriuria; renal function is normal. Renal ultrasound reveals kidneys located lower than expected with fusion of the inferior poles and anteriorly facing renal pelvises. Which of the following is the most appropriate next step in evaluation? A) Begin daily prophylactic antibioticsB) Order a voiding cystourethrogramC) Refer for surgical resection of the fused isthmusD) Schedule renal biopsy to assess for scarring