Nephrology & Urology

Question 1

A 12-year-old presents with bed wetting. She had been “dry” for years and now suddenly has had trouble staying “dry” all night.

What should you consider as one of your first diagnosis to investigate?

Answer 1

Child Abuse

Always consider sexual, physical, or emotional abuse in all voiding disorders. A good bedwetting evaluation in this case could save a child’s life!

Question 2

What is the most common genital problem in newborn males?

Answer 2

Cryptorchidism

Cryptorchidism (undescended testes) occurs in up to 33% of premature boys and in 3–4% of term males. By 1 year of age, the testes have descended in all but 0.3%.

Question 3

Which specific antibody is commonly found in granulomatosis with polyangiitis (GPA; formerly Wegener polyangiitis)?

Answer 3

Anti-Proteinase-3 (PR3)

In 80–90% of patients, GPA is confirmed by ­positive antiproteinase-3 (anti-PR3) antibodies that produce a c-ANCA pattern. The c-ANCA test is sensitive and ­specific for GPA.

Question 4

What is an abnormal dilatation and tortuosity of the testicular vein and pampiniform plexus of the spermatic cord called?

Answer 4

Varicocele

Varicoceles are found in 15% of adolescent boys and are unusual prior to puberty. They are almost exclusively on the left side. Repair these if the boy has atrophy or slow growth of the left testis compared to the right.

Question 5

What is the most common cause of acute renal failure in a previously healthy child?

Answer 5

Hemolytic Uremic Syndrome (HUS)

HUS is a complicated sequence of events that begins with endothelial and glomerular injury and eventually results in microangiopathic hemolytic anemia, thrombocytopenia, and renal insufficiency. 90% are due to preceding diarrhea due to E. coli O157:H7.

Question 6

When should inguinal hernias be repaired?

Answer 6

On Diagnosis

All inguinal hernias should be repaired as soon as possible after diagnosis. Strangulated hernias are a surgical emergency.

Question 7

What is the most common nephrologic cause of gross hematuria in children?

Answer 7

IgA Nephropathy

IgA nephropathy is the most common cause of gross hematuria; it used to be acute poststreptococcal glomerulonephritis (APSGN).

Question 8

What condition is most associated with a very low fractional excretion of sodium (FE_Na)?

Answer 8

Prerenal Acute Kidney Injury (AKI),

a.k.a. Prerenal Azotemia

Prerenal AKI is due to decreased blood flow into the kidneys, with a resulting reduced glomerular filtration rate (GFR). Several factors can cause prerenal AKI, including certain drugs (e.g., diuretics [most common], NSAIDs, and ACE inhibitors), renal artery stenosis, and cirrohsis. FE_Na is very low (< 1%) in prerenal AKI, making it a good 1st test to assess whether the AKI is prerenal or intrinsic. (FE_Na in intrinsic AKI is > 1%.) Interestingly, you can see a low FE_Na in many types of glomerulonephritis (GN) as well.

Question 9

A young boy presents with the following:

• Absence of abdominal wall musculature
• Cryptorchidism
• Dilation of the prostatic urethra, bladder, and ureters

What is the syndrome with these findings?

Answer 9

Prune Belly Syndrome (a.k.a. Eagle-Barrett Syndrome,

Urethral Obstruction Malformation Complex)

Prune belly syndrome occurs in about 1/40,000 boys and is much rarer in girls, who make up only 5% (or 1/800,000) of all cases. The syndrome gets its name from the shriveled, prune-like skin on the infant’s abdominal wall. It can have varied presentations, but the most common is a group with significant anatomical genitourinary anomalies but normal renal function. It can be confused with posterior urethral valves (PUV) in utero.

Question 10

What is the serious CNS complication you worry about with autosomal dominant Polycystic kidney disease?

Answer 10

Berry Aneurysms in the Circle of Willis

If these aneurysms rupture, they can be fatal. Like ADPKD itself, these aneurisms tend to run in specific families.

Question 11

A newborn presents with:

• History of oligohydramnios while in utero
• Low-set ears
• Flat nose
• Retracted chin
• Palpable enlarged kidneys
• Hypertension
• Hepatic fibrosis

What is the most likely diagnosis?

Answer 11

Autosomal Recessive Polycystic Kidney Disease (ARPKD)

ARPKD disease results in bilateral kidney enlargement and transforms collecting ducts into fusiform cysts. Hepatic fibrosis is universal. Oligohydramnios occurs because of intrauterine renal failure. “Potter facies” (low-set ears, flat nose, and retracted chin) is due to decreased amniotic fluid with insufficient lung development. A finding of palpable kidneys is the most common feature of ARPKD, followed by hypertension and recurrent UTIs.

Question 12

What additional vaccines should a child with minimal change nephrotic syndrome receive?

Answer 12

PPSV23

For children with all types of nephrotic syndrome, both pneumococcal vaccines are recommended. Make sure the child has received the recommended PCV13 inoculations, and add PPSV23 in accordance with the CDC immunization schedule.

Question 13

What is the most common congenital anomaly of the penis?

Answer 13

Hypospadias

Hypospadias occurs in 1/300 males and results in the abnormal positioning of the urethral meatus proximal to the tip of the glans. Hypospadias occurs most commonly as an isolated event, and no imaging of the upper GU system is required.

Question 14

A boy presents with:

• Persistent microhematuria
• Proteinuria
• Hypertension
• Sensorineural deafness
• Perimacular pigment changes

He has a maternal uncle with the same disease process.

What is the most likely diagnosis?

Answer 14

Alport Syndrome

Alport syndrome arises from mutations in the genes that encode for Type 4 collagen, which makes up the collagen part of basement membranes of the kidneys, ears, and eyes. About 80% of cases are X-linked dominant. Consider this diagnosis in any child with kidney problems, ocular problems, and hearing loss or a family history of early hearing loss. Affects boys more severely. Girls will only have renal issues (hematuria, ESRD).

Question 15

What is a commonly used potassium-sparing diuretic?

Answer 15

Spironolactone

Spironolactone is an aldosterone antagonist, so it is potassium sparing and hence can also cause acidosis. Triamterene and amiloride are also potassium sparing.

Question 16

What is the risk of undescended testes?

Answer 16

Malignancy

Persistently undescended testes have an increased risk of cancer, especially seminoma—this is why we must fix them. Boys whose testes are still undescended by 6 months of age should be referred for surgical evaluation. Orchiopexy is likely to be performed between 6 and 18 months of age to decrease the risk of infertility and malignancy.

Question 17

What is the most common cause of hydronephrosis in infancy and childhood?

Answer 17

Ureteropelvic Junction Obstruction (UPJ)

UPJ is frequently found on prenatal ultrasound and is suspected when only the renal pelvis is dilated but the ureter is not.

Question 18

What are the most common causes of urinary obstruction in male infants?

Answer 18

Posterior Urethral Valves (PUV)

PUVs are a pair of obstructing leaflets in the prostatic urethra. PUVs are the most common cause of obstructive uropathy that leads to kidney failure in childhood. They occur in about 1/5,000 males. Most cases are discovered in utero with bilateral hydroureteronephrosis.

Question 19

A 14-year-old girl presents for evaluation. She had a urine dipstick done at school by the school nurse and was told that it showed “protein.” She is not hypertensive and has no family history of renal disease. She is growing well and actually just hit her growth spurt in the last 6 months. Repeat urinalysis in your office shows proteinuria again. Otherwise, the urinalysis is normal.

What diagnosis should you consider first?

Answer 19

Benign Orthostatic Proteinuria

This can occur in up to 10–20% of adolescents (particularly girls), especially during the growth spurt. Check supine and upright urine proteins for diagnosis. (The proteinuria reverts to normal values when the patient is supine.) A first morning urine specimen is helpful in diagnosis. Benign orthostatic proteinuria is as it says, a benign condition, not associated with pathology.

Question 20

What is it called when the foreskin cannot be retracted?

Answer 20

Phimosis

Physiologic phimosis is the most common cause, followed by iatrogenic injury from forcible retraction. Most foreskins should easily be retracted by 4 years of age.

Question 21

Which type of renal tubular acidosis (RTA) most commonly causes renal stones?

Answer 21

Type 1 RTA (Distal)

The renal stones associated with Type 1 RTA are probably caused by decreased citrate excretion and hypercalciuria. Amphotericin B is one of the most common causes of Type 1 RTA. High urine pH > 5.5 (alkalotic). All others have normal urine pH.

Question 22

• Autosomal dominant
• Hypoplasia or absence of the patellae
• Dystrophic nails
• Dysplasia of the elbows
• Renal disease with microhematuria and mild proteinuria, but 10% of cases progress to end-stage renal disease (ESRD)

What syndrome has these findings?

Answer 22

Nail-Patella Syndrome

There is no specific therapy for the nephropathy of nail-patella syndrome, but renal transplant appears to be effective in patients who progress to ESRD. This is a rare disorder in practice, but it is commonly seen on exams!

Question 23

What are the most common sites for thromboses in a child with nephrotic syndrome?

Answer 23

Renal Vein and Sagittal Sinus

In children with nephrotic syndrome, these are the most common locations for clots, followed by the pulmonary and femoral arteries. Almost all nephrotic children have a hypercoagulable state, and about 20% will have a thrombotic event that is clinically silent!

Question 24

How do you calculate the serum anion gap (AG)?

Answer 24

AG = Na⁺ – (Cl^– + HCO₃^–)

Make sure you do the operations correctly. If you subtract the bicarbonate from the chloride and then subtract that answer from the sodium, you will get the wrong answer!

Remember, physiologically there is no true “gap”; the term just refers to the usual amount of unmeasured anions in serum (or urine).

Question 25

A newborn male presents with retractile testes that can be pulled down into the scrotum, but on letting go, they end back up superiorly.

What should be done at this point?

Answer 25

Watchful Waiting

Almost all retractile testes eventually end up in the scrotum, so no further management is necessary.

Question 26

You find a hydrocele on a 2-month-old.

When should the child undergo repair if it persists?

Answer 26

1 Year of Age

Hydroceles that last past 1 year if age should be surgically repaired. Non-communicating hydroceles usually resolve before the 1^st birthday.

Question 27

What should you consider if you find eosinophils on a UA?

Answer 27

Allergic Interstitial Nephritis

Eosinophilia on a urinalysis should make you think of drug-induced hypersensitive-mediated interstitial nephritis.

Question 28

What organism is commonly associated with staghorn calculi?

Answer 28

Proteus

 Struvite kidney stones are composed of magnesium ammonium phosphate and calcium carbonate apatite crystals. They grow quickly and often cause staghorn calculi. Think infection when you see these. Proteus is the most common organism associated with development of kidney stones, particularly staghorn calculi. Other organisms that can do this include Pseudomonas, yeast, and Staphylococcus. (Remember the charming mnemonic PPYS, pronounced “piss.”)

Question 29

Does antibiotic therapy prevent acute post-streptococcal glomerulonephritis?

Answer 29

No

APSGN follows after infection with specific ­nephritogenic strains of Streptococcus pyogenes (group A β-hemolytic Strep). The risk of this occurring is believed to be ∼ 10–15%. While antibiotics for group A streptococcal infection do not prevent APSGN, they do prevent rheumatic fever if given for a pharyngeal strain.

Question 30

• Autosomal dominant
• Multiple family members with hematuria and/or RBC casts, but no history of renal failure

Name the syndrome.

Answer 30

Thin Basement Membrane Nephropathy

(a.k.a. Benign Familial Hematuria)

Thin basement membrane nephropathy is an AD disease with hematuria but no long-term sequelae of renal disease. Biopsy of the kidney reveals a very thin basement membrane. No treatment is required and prognosis is good. However, long-term surveillance is required because some patients diagnosed with this condition go on to develop proteinuria and ­progressive renal failure over time.

Question 31

A boy is born with hypospadias.

Should he have a circumcision?

Answer 31

No

Neonatal circumcision should not be performed on a boy with hypospadias because hypospadias repair uses preputial skin. Hypospadias is typically an isolated event and does not require genitourinary workup.

Question 32

What type of anion gap is associated with all renal tubular acidoses (RTAs)?

Answer 32

Normal Anion Gap

RTA is a metabolic acidosis typically caused by a defect—often genetic—in renal tubule function due to the inability of the kidney to maintain high enough bicarbonate. All 3 types of RTA have a normal serum anion gap—i.e., all are hyperchloremic. Type 4 is the only one with hyperkalemia.

Question 33

You start an aminoglycoside in a child. 8 days later his creatinine rises and his FE_Na is not low.

What is the mechanism by which the aminoglycoside likely caused acute kidney injury (AKI)?

Answer 33

Acute Tubular Necrosis (ATN)

ATN is the most common cause of intrarenal AKI (about 75%!) in adults and is very common in children. Aminoglycosides are one of several types of drugs that can induce ATN. They cause proximal tubule damage resulting in nonoliguric ATN. ATN is usually delayed 7–10 days after starting therapy, and early therapeutic levels are not a guarantee of safety!

Question 34

What is entrapment of a phimotic foreskin behind the glans of the penis called?

Answer 34

Paraphimosis

Paraphimosis results in edema and swelling of the glans and foreskin. This is a medical emergency that can cause necrosis! Reduction (returning the foreskin to its normal position covering the glans) often requires sedation and local anesthesia.

Question 35

How do you calculate the osmolar gap?

Answer 35

Measured Osmolality – Calculated Osmolality

Calculated Osmolality = 2[Na⁺] + (BUN/2.8) + (Glucose/18)

The osmolality of the blood is determined mainly by concentrations of sodium, glucose, and urea. The OG is the difference between the measured serum osmolality (from the lab) and a calculated estimation of what the osmolality ought to be—if the only effective osmoles present are the normal ones (Na+, glucose, and urea). A normal OG is < 10 mOsm/kg. An extremely high OG (> 25 mOsm/kg) is almost always due to toxic alcohol poisoning.

Question 36

A patient presents with:

• Polyuria
• Polydipsia
• Anemia
• FTT
• Salt-losing nephropathy—with no signs of nephrotic or nephritis syndrome
• The patient also has these extrarenal manifestations:
  
  • Inability to perform horizontal eye movements
  • Retinitis pigmentosa (Senior-Loken syndrome)
  • Cerebellar aplasia with coloboma of the eye (Joubert syndrome)

What is the most likely diagnosis?

Answer 36

Juvenile Nephronophthisis Type 1 (NPH1)

NPH1 is an AR disease that is very rare. The strange thing to remember is that this is a salt-losing nephropathy without nephrotic or nephritic syndrome. Renal ultrasound shows poor differentiation between the cortical and medullary areas of the kidney. After 9 years of life, cysts are common at the corticomedullary border. End-stage renal disease (ESRD) occurs, on average, by 13 years of age.

Question 37

A patient presents with:

• High anion gap metabolic acidosis (HAGMA)
• High osmolal gap (OG)
• Calcium oxalate crystals in the urine

What is the most likely ingestion?

Answer 37

Ethylene Glycol (Antifreeze)

Ethylene glycol, propylene glycol, and methanol are the classic toxic alcohols that present with a HAGMA and a high OG. Here are some facts on each:

• Ethylene glycol: Most of its effects are kidney related, and you will see calcium oxalate crystals in the urine.
• Propylene glycol: Used as a solvent for intravenous lorazepam (and other drugs) and is an FDA-approved food sweetener. Continuous infusion or repeated large IV doses of lorazepam or sustained intestinal absorption of propylene glycol can cause severe lactic acidosis.
• Methanol: Metabolizes to formic acid, a substance that is directly toxic to the optic nerve. Visual symptoms are the key clue.

Question 38

An 8-year-old boy presents with:

• Severe sore throat
• Cola-colored urine
• Hypertension

What is the most likely diagnosis?

Answer 38

IgA Nephropathy (Berger Nephropathy)

The key here is that the sore throat is occurring at the same time as the hematuria; thus, this is most likely IgA Nephropathy - remember that, with acute post-streptococcal glomerulonephritis, you have a latent period of 1-2 weeks!

Question 39

A 20-year-old male presents with anti-glomerular basement membrane (anti-GBM) disease.

On renal biopsy, what will be seen deposited in the glomerular basement membrane?

Answer 39

IgG and C3

Finding crescentic nephritis and linear deposits of IgG and C3 in the GBM on renal biopsy confirms a diagnosis of anti-GBM disease. You can also find anti-GBM antibody in the plasma of 90% of patients.

Question 40

When should you begin yearly screening for albuminuria in patients with diabetes mellitus (DM) Type 1? Type 2?

Answer 40

Begin 3–5 Years after Initial Diagnosis;

Screen Yearly after Initial Diagnosis

For patients with DM Type 1, because you generally know when they have onset of the disease, you can wait several years before beginning annual albuminuria screens. For those with DM Type 2, because you do not know how long they have had the disease, start screening yearly after the initial diagnosis.

Question 41

A 17-year-old high school football player presents in August with:

• Severe weakness
• Nausea/vomiting
• Serum CK is markedly elevated.
• High serum potassium
• Creatinine is 3.1 mg/dL with a mildly elevated BUN.
• U/A is heme positive but without RBCs.
• Urine myoglobin is present.
• Muddy-brown casts in the urine

What is the diagnosis?

Answer 41

Rhabdomyolysis

Rhabdomyolysis is due to muscle trauma, strenuous exercise, seizures, heat stroke, severe volume contraction, cocaine use, hypophosphatemia, and severe hypokalemia. It can lead to acute tubular necrosis.

Question 42

What is the organism most commonly associated with hemolytic uremic syndrome (HUS)?

Answer 42

Escherichia coli O157:H7

Nearly 90% of children with HUS have a preceding diarrheal illness due to E. coli O157:H7, which produces a Shiga-like toxin.

Question 43

A boy presents with a history of hematuria at the end of urinating, evidenced by spotting of blood in the underwear. Physical examination is normal. Ultrasound is completely normal.

What is the most likely diagnosis?

Answer 43

Urethrorrhagia

Urethrorrhagia occurs only in boys. The process is self-limited and requires no specific therapy but can take up to a year or longer to resolve. The symptoms are usually intermittent and recurrent.

Question 44

What is the best way to manage edema in a child with minimal change nephrotic syndrome (MCNS)?

Answer 44

Salt Restriction

With MCNS, it is vital to provide supportive and symptomatic care. Manage edema with salt restriction. Fluids can be restricted, but generally this is not necessary; defer the use of diuretics except in severe cases.

Question 45

Which RTA is associated with a high potassium?

Answer 45

Type 4 RTA (Distal)

Type 1 RTA has low potassium and Type 2 RTA can have low-to-normal potassium. Only Type 4 RTA is associated with elevated serum potassium.

Question 46

An 8-year-old boy presents with:

• History of documented streptococcal pharyngitis 10 days ago, treated with IM penicillin
• He presents today with edema and cola-colored urine.

What do you expect his complement levels (C3 and C4) to be?

Answer 46

C3: Low, Usually Very Low

C4: Likely Normal or Mildly Low

The boy has acute poststreptococcal glomerulonephritis (APSGN), and the key laboratory finding is a low C3 level, which will remain low for 2–12 weeks (the C3 levels eventually normalize by 6 weeks). Contrast this with IgA nephropathy, where the hematuria occurs concurrently with the infection (no latency) and the C3 level will be normal. The latency period between pharyngitis and APSGN is 1–2 weeks; with skin infection, the latency is 3–6 weeks.

Question 47

What is the most common disease of autosomal dominant inheritance in the U.S.?

Answer 47

Autosomal Dominant Polycystic Kidney Disease (ADPKD)

The prevalence of ADPKD in the U.S. is 1–2 per 1,000 births. End stage renal disease (ESRD) generally doesn’t develop until 50–60 years of age. For children who have parents with the disease, a single cyst on a kidney in childhood is highly predictive of development of ADPKD as an adult.

Question 48

What is the calculation for the urine anion gap (UAG)?

Answer 48

UAG = Na⁺ + K⁺ – Cl^–

Normal anion gap metabolic acidosis (NAGMA; a.k.a. hyperchloremic acidosis) is caused by a loss of HCO3^–, with a commensurate increase in Cl^– (the Cl^– is increased to maintain electrical neutrality). NAGMA typically occurs via the kidney (renal tubular acidosis [RTA]) or the GI tract (diarrhea). UAG is used to differentiate between these 2 as the cause of NAGMA:

• UAG is positive with NAGMA due to RTA.
• UAG is negative with NAGMA due to GI losses. Remember: neGUTive—negative UAG in bowel cases.

Question 49

A 5-year-old boy with a history of URI 1 week ago presents with:

• Purpuric rash on the buttocks, abdomen, and lower extremities
• Abdominal pain
• Arthralgias
• Glomerulonephritis with IgA deposition

What is the most likely diagnosis?

Answer 49

Henoch-Schonlein Purpura (HSP)

HSP peaks between 4 and 5 years of age. The renal lesion on histological exam looks just like IgA nephropathy. 90% have full recovery of renal function; however, 3–4% develop end stage renal disease (ESRD), which can occur anywhere from a few months to several years after onset. Another 5% have evidence of chronic renal damage.

Question 50

What type of casts are seen in acute tubular necrosis (ATN)?

Answer 50

Large, Muddy-Brown Granular Casts

Hallmark urine findings in ATN include red or brown urine with large, muddy-brown granular casts (not always present). Oliguric ATN commonly resolves in 1–4 weeks.

Question 51

What is the most common cause of nephrotic syndrome in children?

Answer 51

Minimal Change Nephrotic Syndrome

(MCNS; a.k.a. Minimal Change Disease)

MCNS is the most common type of nephrotic syndrome in childhood (60−85% of cases in patients < 10 years of age and 65% of pediatric cases overall). It is almost always idiopathic but has been associated with Hodgkin disease, NSAIDs, and systemic immune-mediated diseases. A history of atopy occurs in 30–60% of affected children.

Question 52

A 4-year-old African-American girl presents with:

• Vaginal spotting in her underwear
• Physical exam shows an everted, hemorrhagic, donut-shaped periurethral mass.

What is the diagnosis?

Answer 52

Urethral Prolapse

Urethral prolapse occurs when the urethral mucosa completely extrudes through the external meatus. It is most commonly seen in African American girls between 4 and 10 years of age. Predisposing symptoms include coughing, constipation, trauma, and urinary or vaginal infections. Manage conservatively with topical estrogen cream, applied twice daily following a sitz bath. This often leads to resolution within 2–4 weeks. Surgery is required only if there is associated evidence of necrosis.

Question 53

What is the most common cause of priapism?

Answer 53

Sickle Cell Disease (SCD)

Priapism is a painful, unremitting erection in which the corpora cavernosa is rigid, but the glans and corporus spongiosum are flaccid. It is sometimes the presenting symptom of SCD!

Question 54

Which type of renal tubular acidosis (RTA) is associated with Fanconi syndrome?

Answer 54

Type 2 RTA (Proximal)

Type 2 RTA is also associated with amino acid problems, heavy metal exposure, and use of outdated tetracycline.

Question 55

What is the most common cause of obstructive uropathy that leads to renal failure in childhood?

Answer 55

Posterior Urethral Valves (PUV)

PUVs are a pair of obstructing leaflets in the prostatic urethra of newborn males. Most cases are discovered in utero with bilateral hydroureteronephrosis. Do a VCUG after birth to make the diagnosis. These infants require immediate bladder drainage. Despite treatment (removal of the valves), damage is already done, and up to 30% of these boys will develop end-stage renal disease (ESRD) during childhood.