Clinical Reasoning-Congenital:Genetic Kidney Disease Flashcards
What kidney function would be impaired if you saw cysts on an imaging study? What kidney function would be impaired if cysts were present but you couldn’t see them?
The ability to filtrate properly would be affected if you could see the cysts because you can only see cysts in the cortex. The ability to reabsorb would be affected if you couldn’t see them because thats mostly what happens in the medulla and you can’t see cysts in the medulla.
A 7 year old female presents to the ED with a two day history of right flank pain. She has no fever, dysuria or urinary urgency. She has an occasional headache. Her BP is 120/85, elevated for a child and she had hematuria after falling in gymnastics two times. Her mother has bilateral cystic kidney disease and two brothers are on dialysis. What is your diagnosis?
Her family history tells us that she most likely has the dominant form of polycystic kidney disease. Headache from possible berry aneurism? Look for possible mitral valve prolapse?
Why do you want to analyze the morphology of RBCs in a patient’s urine?
Normal RBCs in the urine originate from somewhere downstream from the glomerulus. RBCs get distorted going through the glomerulus. RBCs in the urine tell you where kidney disease is originating from.
What is a normal GFR?
100-120
How do you determine GFR?
Creatinine levels. It is freely filtered and freely excreted in the urine.
A patient with suspected renal disease comes to see you. Ultrasound reveals cysts and urinalysis reveals normal-appearing RBCs. Where are these cysts forming?
You know they’re in the cortex because you can see them. You also know they are in the PCT because the RBCs are normal. If the pathology was in the glomerulus the RBCs would look abnormal.
What portion of the kidney is responsible for sensing pain when you have pyelonephritis?
The kidney stretches and causes the capsule to stretch, which is the only innervated portion of the kidney.
How do you diagnose autosomal dominant polycystic kidney disease?
Patients < 2 years w/ 2 cysts. Patients > 3 years w/ 3 cysts. Patients under 2 years w/family history.
Why would you ultrasound the kidneys of the parents of a child with a cyst?
Autosomal dominant PCKD will cause cysts to form in 98% kidneys of adults before the age of 30.
What gene causes people to go into renal failure by age 40-50? What gene causes people to go into renal failure by age 60?
40-50=PKD1. 60=PKD2. They both code for polycystin that deposits in the renal parenchyma.
What are common complications in patients with PCKD? What complications are rare?
Hematuria from cyst rupture. UTIs. Rare complications include cysts in other organs, berry aneurisms, mitral valve prolapse and kidney stones.
A mother brings her 2 year old son to come see you. She has a radiograph that shows a large right kidney and constipation. What information do you want in order to determine if the child has kidney pathology?
High BP? High creatinine? Proteinuria?
A 2 year old patient comes to your office with an abnormal x-ray. One of the kidneys is enlarged and the other kidney’s ultrasound is seen below. Why is the other kidney enlarged?
This child has metaplastic kidney disease (agenesis of one kidney) and the other kidney is enlarged to compensate.
What can cause metaplastic kidney disease?
Malformations of the uteric bud.
When would you remove a dysplastic kidney?
Uncontrolled hypertension and recurrent infection (these patients have a higher chance of vesicouretal reflux)
You visit a 2 day old infant with bilateral large kidneys and increased creatinine levels. She is jaundiced, intubated and has a ventilator on high settings. Her blood pressure is elevated and urine output is low. Why would this child need to be on a ventilator if her kidneys have the pathology?
Oligohydramnios: decreased amniotic fluid is a result of decreased kidney function and the babies need that amniotic fluid for the lungs to develop properly.
What is Potter’s sequence?
Oligohydramnios, pulmonary hypoplasia and enlarged echogenic kidneys.
Why do kids with metaplastic kidney disease never become potty trained once they make it out of the hospital?
The damage is done to the medulla where the distal tubules and collecting ducts are. ADH works on the distal tubules and collecting ducts, but since they’re damaged water reabsorption does not occur and the kids pee out much of what they drink.
What genetic factors cause metaplastic kidney disease?
Autosomal recessive PCKD from PKHD1 which encodes fibrocystin.
Why might babies with metaplastic kidney disease present with jaundice and hematemesis?
PKHD1 makes fibrocystin, which causes fibrosis of the liver. This causes esophageal varices which may rupture and present as hematemesis.
How do you diagnose metaplastic kidney disease?
Enlarged echogenic kidney with poor corticomedullary differentiation + absence of cysts in both parents and/or hepatic fibrosis and/or affected sibling and/or consanguinity
What complications exist when babies are born with metaplastic kidney disease?
Pulmonary hypoplasia, hepatic fibrosis, renal failure and severe hypertension.
A 13 year old female presents with polyuria, enuresis (bedwetting), poor growth and high blood pressure. UA shows proteinuria. She has elevated creatinine and BUN. Radiology shows small kidneys bilaterally and poor corticomedullary differentiation. What is your diagnosis? What gene is responsible for it?
Medullary polycystic kidney disease (Senior-Loken syndrome) is the most common congenital cause of a teenager going to renal failure. It is from the NPH gene which codes nephrocystin.
