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Polycystic Kidney Disease (PKD), Part 1

Neda Frayha, MD and Terry Watnick, MD
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Autosomal dominant polycystic kidney disease is broken down into two main subtypes: PKD-1 and PKD-2.  PKD-1 leads to renal impairment approximately 20 years before PKD-2.  While there is a 50% chance that the offspring of a parent with PKD will have the condition, routine screening before the age of 18 is not recommended due to to potential emotional or psychological impact and impact on insurability. Extra renal manifestations include polycystic liver disease and intracranial aneurysms. Hypertension management is key, with ACE or ARB being first line to keep BP below 130/80. Tolvaptan, a vasopressin 2 receptor antagonist, has recently been approved in the European Union, Canada, and Japan for the treatment of PKD, and it may be approved soon in the United States.

Pearls:

  • PKD is the most common inherited form of renal disease that is characterized by enlarged kidneys and cysts eventually leading to renal failure.

  • Routine screening is not recommended because currently there is no treatment and it may cause unnecessary anxiety.

  • Typical presentations include back pain and hematuria after physical contact.

  • Liver cysts and brain aneurysms are the common extrarenal manifestations to be on the lookout for.

  • Supportive care includes blood pressure with an ACE/ARB, monitoring BUN/Cr at least yearly, encouraging high fluid intake in those with normal kidney function and early referral to a nephrologist for transplant consideration.

  • UTI in someone with PKD should be treated as complicated, meaning 7-10 days of lipophilic antibiotic such as ciprofloxacin or trimethoprim-sulfamethoxazole.

  • Vasopressin-2 receptor antagonists are on the horizon as a  treatment option  but will likely be reserved for those with rapidly progressive disease.

 

  • What is PKD? Most common inherited form of renal disease. Enlarged kidneys and cysts develop throughout one’s life and eventually lead to renal failure.

    • Autosomal dominant (50% chance of passing it on)

      • PKD1 on chromosome 16 (80% of mutations) → average individual will develop kidney failure in their early 50’s

      • PKD2 on chromosome 4 (20% of mutations) → milder, develop kidney failure 20 years later in 70’s.

    • Autosomal recessive form is much less common (and we don’t cover it in this podcast). You may see the more severe form of this  in children.

  • Who should we screen? It is not recommended.

    • There’s no treatment for the disease other than treating high blood pressure.

    • Even if you know a patient’s parent has PKD, diagnosing them with the disease will then give them a pre-existing condition and may cause unnecessary emotional trauma.

    • Also, someone with PKD is not born with cysts and they accumulate over a lifetime via a second hit mechanism. Therefore, screening someone in their 20’s may give a false negative.

  • How many people does it affect?

    • Between 1 in 500 and 1 in 1000, which is about 600,000 in the US. No predisposition for sexes or race/ethnicity.

  • What is the most common presentation?

    • Most frequent presentation is back pain, high blood pressure in a young person or gross hematuria especially after some kind of physical contact.

    • ~15% of people with PKD don’t have an identifiable family history:

      • May have been mild in parents or another illness led to their demise

      • 5-10% of cases arise as a result of de novo mutations

  • Extrarenal manifestations?

    • Polycystic liver disease: 80%, especially for women. It is thought to be hormonally-mediated so it is recommended women with PKD avoid exogenous hormone therapy.

    • Intracranial aneurysms: 8-12%, rates are higher in those with a positive family history (18-25%) → screening is recommended in those with family history or those where rupture might place a lot of people at risk (airline pilot, etc), unexplained neurological symptoms and for purposes of reassurance.

  • How would you work-up the person with symptoms concerning for PKD?

    • Renal ultrasound: isolated renal cysts are common

    • Referral to nephrology

    • DNA testing also available but very expensive and generally not necessary

  • Monitoring in PKD?

    • Routine ultrasounds probably not necessary as you can’t do much as we know the disease progresses with time. However, if the patient is having worsening symptoms then it might be necessary to see if there is a cyst that needs to be addressed.

    • Blood pressure control is key. First-line treatment is blockers of renin-angiotensin system (RAAS) - ARB and ACE-I. It is thought the cysts in the kidneys compress the intrarenal vasculature and rev up the RAAS.

      • HALT trial looked at BP control with combo ARB/ACE-I and found no benefit.

      • For those with GFR > 60, goal is <130/80; otherwise, consider a goal <110/70 for those who can tolerate it (ie: young and otherwise healthy)

    • BUN/Cr at least yearly and if not more just as in a person with hypertension

    • Once they develop CKD, they should be co-managed with a nephrologist.

  • Treatment?

    • Other than managing blood pressure and CV risk (lipids), there have been no treatments to date.

    • Tolvaptan (vasopressin-2 receptor antagonist) has been shown to decrease progression of kidney size (measured by MRI)  with a modest effect on slowing renal function. It has been approved in Canada, EU and Japan for rapidly-progressing PKD.

      • Causes patients to urinate 5-6 liters of water per day, so they have to drink a lot of water.

    • Patients are also advised to drink 2-3 liters per day if they have normal kidney function because that also suppresses vasopressin.

    • Exercise/sports that are low impact is probably safe.

      • If a cyst does bleed (generally presents with hematuria), 90% of the time it resolves with rest, lots of fluids to prevent clot formation, avoidance of activities like lifting that may precipitate bleeding, and avoidance of aspirin or medications that will cause bleeding.

    • Referral for transplant as soon as possible.

  • Treatment of UTI in those with PKD?

    • Treat based on urinalysis, culture and symptoms.

    • Ciprofloxacin or trimethoprim-sulfamethoxazole are lipophilic so have good penetration into the cysts.

Minimum duration is 7-10 days because it is “complicated” and not “uncomplicated”, which is generally treated with 3 days of antibiotics.

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