Nephrology Flashcards
Define Acute Kidney Injury
A rapid decline in renal function with an increase in serum creatinine.
Define RIFLE
- Risk
- Injury
- Failure
- Loss
- ESRD
Define RISK from RIFLE
A 1.5 fold increase in the serum creatinine or GFR decrease by 25% or urine output <0.5 mL/kg/hr for 6 hours.
Define INJURY from RIFLE
Twofold increase in serum creatinine of GFR decrease by 50% or urine output of <0.5 mL/kg/hr for 12 hours
Define FAILURE from RIFLE
Threefold increase in the serum creatinine or GFR decrease by 75% or urine output of <0.5 mL/kg/hr for 24 hours or anuria for 12 hours.
Define LOSS from RIFLE
complete loss of kidney function requiring dialysis for more than 4 weeks
Define ESRD from RIFLE
Complete loss of kidney function requiring dialysis for more than 3 months.
What are the 2 most common findings in someone with AKE?
Weight gain and edema. This is due to a positive water and sodium balance.
Define Azotemia
Elevated BUN an Cr
What are the 2 most common causes of death in AKI?
Infection and cardiorespiratory problems.
Define prerenal failure
Caused by a decrease in systemic arterial blood flow or renal perfusion. Most common cause of AKI and potentially reversible.
What are some causes of prerenal failure?
- CHF
- Hypovolemia
- Hypotension
- Renal arterial obstruction
- Cirrhosis/Hepatorenal syndrome
- NSAIDs, ACE-inhibitors, and cyclosporine
What are the things that you want to monitor in a patient with AKI?
- Daily weights, intake and output
- Hb and Hct for anemia
- Signs of infection
- Serum electrolytes
- BP
Describe the pathophysiology of prerenal AKI
-Renal blood flow decrease enough to lower the GFR which leads to decreased clearance of metabolites (BUN, Cr, uremic toxins). However, since the renal parenchyma is undamaged, tubular function and concentrating ability remains intact. Therefore the kidney responds appropriately conserving as much sodium and water as possible.
What are the lab findings in prerenal AKI
- Oliguria: to preserve volume
- Increased BUN:Cr ration: >20:1
- Increased urine osmolality: >500 mOsm/kg because the kidney is able to resorb water
- Decreased urine Na+: <20 mEq/L with FeNA <1% because Na+ is avidly reabsorbed
- Increased urine:plasma Cr ratio >40:1 because much of the filtrate is reabsorbed.
Define intrinsic renal failure
Kidney tissue is damaged such that the GFR and tubular function are significantly impaired. THe kidneys are unable to concentrate urine effectively.
What are some causes of intrinsic renal failure?
- Tubular disease (ATN): can be caused by ischemia, nephrotoxins
- Glomerular disease: (Acute glomerulonephritis) Goodpastures, Wegeners, Post-strep GN, lupus
- Vascular disease: renal artery occlusion, HUS, TTP
- Interstitial Disease: allergic interstitial nephritis
What lab abnormalities are seen in Rhabdo?
-hyperkalemia, hypocalcemia, hyperuricemia, elevated CPK
How do you treat rhabdo?
-IV fluids, mannitol, bicarb (which drives k+ back into cells)
What are the lab findings seen in intrinsic renal failure?
- BUN:Cr
- Urine Na+
- FeNa
- Urine Osmolality
- urine:plasma cr ratio
- Decreased BUN:Cr ratio (<20:1) in comparison with prerenal failure. Both BUN and Cr are still elevated but less urea is reabsorbed in comparison with prerenal.
- Urine Na+ increased >40 mEq/L
- FeNA >2-3% Because Na+ is poorly reabsorbed
- Decreased urine osmolality <350 mOsm/kg because renal water absorption is impaired
- Decreased urine:plasma Cr ratio <20:1 because filtrate cannot be reabsorbed
What are two causes of acute tubular necrosis?
- Ischemic AKI 2/2 to shock, hemorrhage, sepsis or DIC which leads to death of tubular cells.
- Nephrotoxic AKI which is injury 2/2 substances that directly injury renal parenchyma and result in cell death.
What are some agents that can cause nephrotoxic AKI?
- Abx: aminoglycosides and Vanc
- Radiocontrast agents
- NSAIDs
- Poisons
- Myoglobinuria
- Hemoglobinuria
- Chemo: cisplatin
- Kappa and gamma light chains (MM)
Define postrenal AKI
Obstruction of any segment of the urinary tract with an intact kidney can cause increased tubular pressure therefore urine cannot be excreted and this leads to a decreased GFR. Blood supply and renal parenchyma are intact. note that the kidneys must be obstructed for the creatinine to rise.
What are some causes of postrenal AKI?
- BPH
- obstruction of solitary kidey
- Nephrolithiasis
- Obstructing neoplasm
- Retroperitoneal fibrosis
- Ureteral obstruction-must be bilateral
What are the 3 phases of ATN?
- Onset
1. ) Oliguric phase
2. ) Diuretic phase
3. ) Recovery phase
What are hyaline casts associated with?
Prerenal failure
What are RBC casts associated with?
Glomerular disease
What are WBC casts associated with?
renal parenchymal inflammation
What are fatty casts associated with?
nephrotic syndrome
What are muddy brown casts assocaited with?
ATN
Lists the complications of AKI
- Hyperkalemia
- Metabolic acidosis: decreased H+ excretion
- Hypocalcemia
- +/- Hyponatremia
- Hyperphosphatemia
- Hyperuricemia
- Uremia
- Infection
What are the general treatments for AKI?
- Avoid medications that decreased RBF or are nephrotoxic
- Normalize the fluid imbalance
- Adjust the medication doses for the level of renal function
- Correct electrolyte disturbances
- Optimize cardiac output
- Dialysis if necessary
Treatment for prerenal AKI
- Treat the underlying disorder
- Give NS to maintain euvolemia and restore BP (unless they have edema or ascites)
- Eliminate offending agent s
- If unstable Swan-Ganz monitoring for accurate assessment of intravascular volume
Treatment for intrinsic AKI
- Once ATN develops, therapy is supportive. Eliminate the cause/offending agent.
- If oliguric, a trial of furosemide may help to increase urine flow and improve fluid balance.
Define Chronic Kidney Disease
Decreased kidney function (GFR <60) or kidney damage (functional or structural) for at least 3 months.
What are the most common causes of CKD?
- Diabetes (#1)
- HTN (#2)
- Chronic GN
What is uremia?
-The clinical syndrome associated with the accumulation of nitrogenous wastes due to impaired renal function.
What are the cardiovascular manifestations of CKD?
- CHF
- HTN: decreased GFR stimulates RAAS which leads to increased BP
- Pericarditis
What are the neurologic manifeststions of CKD
-Hypocalcemia
=Lethargy, somnolence, confusion, neuropathy, uremic symptoms
What are the hematologic manifestations of CKD?
- Normocytic normochromic anemia
- Bleeding secondary to platelet dysfunction (uremia)
What are the calcium/phosphate disturbances that can occur with CKD?
-Hyperphosphatemia
-Hypocalcemia
–> both lead to increased PTH release (secondary hyperparathyroidism)
Secondary hyperparathyroidism can cause renal osteodystrophy which causes weakening of bones and possibly fractures.
-Vascular calcifications
What tests do you want to order to diagnose CKD?
- UA
- Cr and GFR
- CBC (anemia, thrombocytopenia)
- Serum electrolytes)
- Renal ultrasound
Treatment for CKD
- Low protein diet
- Low salt diet
- Restrit potassium phosphate, and magnesium intake
- ACEi’s or ARBS
- BP Control
- Glycemic control
- Smoking cessation
- Correction of anemia and electrolyte abnormalities
- -Dialysis or transplant if necessary
What are 3 life threatening complications that can occur with CKD?
- Hyperkalemia: EKG!
- Pulmonary edema: 2/2 to volume overload
- Infection: pneumonia, UTI, sepsis
Absolute indications for Dialysis
A-acidosis
E-electrolytes: hyperkalemia (sever and persistent)
I-ingestion: methanol, ethylene glycol, lithium, aspirin
O-overload: not managed by other means
U-uremia: uremic pericarditis!
Complications of hemodialysis
- Hypotension
- First use syndrome
- Anticoagulation complications
- Infection of the vascular access site
- Amyloidosis of beta-2 microglobulin
Complications of peritoneal dialysis
- Hyperglycemia
- Hyperlipidemia
- Abdominal/inguinal hernia 2/2 to increased intraabdominal pressure
- Protein malnutrition
How does ADPKD present?
- Abdominal pain
- Hematuria
- HTN
- Flank mass
Complications of ADPKD
- Intracerebral berry aneurysm
- Infection of the renal cysts
- Renal failure
- Kidney stones
- heart valve abnormalities (MV prolapse)
- Cysts in liver, spleen, pancreas, bone
- Diverticula
- Hernias
How do you diagnose ADPKD
-U/S, CT or MRI
Treatment of ADPKD
- Drain cysts
- Transplant
- Treat infection
- Control HTN
What is the pathology of ARPKD?
It ic characterized by cysts predominantly in the renal collecting ducts as well as hepatic fibrosis.
Clinical picture of ARPKD
- Hepatic involvement is always present
- HTN
- Enlarged kidneys
- Pulmonary hypoplasia/insufficiency
- Potters Syndrome
- Oligohydramnios in mom
What is medullary sponge kidney
- it is characterized by cystic dilation of the collecting ducts
- Thought to be associated with hyperparathyroidism and parathyroid adenoma
What is the most common cause of secondary HTN?
-Renal artery stenosis
What are the two main causes of renal artery stenosis?
- Fibromuscular dysplasia
- Atherosclerosis
Clinical features of renal artery stenosis
- HTN: sudden onset in someone w/o fam hx, resistent to tx
- Decreased renal function
- abdominal bruit
How do you diagnose renal artery stenosis?
- Renal arteriogram but be careful with contrast dyes!
- MRA
- Duplex doppler u/s
Treatment of renal artery stenosis?
-Revascularization with percutaneous transluminal renal angioplasty
-Surgery (bypass)
conservative medical therapy (ACE-is, CCBs)
In what situations might you see renal vein thrombosis?
-Nephrotic syndrome, invasion of the renal vein by RCC, trauma, pregnancy/OCPs, extrinsic compression by retroperitoneal fibrosis, aortic aneurysm, lymphadenopathy) or severe dehydration in infants.
Define hypertensive nephrosclerosis
Systemic HTN increases capillary hydrostatic pressure in the glomeruli leading to benign or malignant sclerosis.
Define benign nephrosclerosis
Thickening of the glomerular afferent arterioles develops in patients with long standing HTN
Define malignant nephrosclerosis
This can develop in a patient with long standing or benign HTN or in a previously undiagnosed person. It is characterized by a rapid decrease in renal function and accelerated HTN due to diffuse intrarenal vascular injury.
Symptoms of benign nephrosclerosis
- Moderate increase in Cr levels
- Microscopic hematuria
- Mild proteinuria
Symptoms of malignant nephrosclerosis
- Markedly elevated BP
- Rapid increase in Cr, proteinuria, hematuria
- RBC and WBC casts in urine, maybe nephrotic syndrome
- MAHA may also be present
What are the 4 classifications of proteinuria?
- Glomerular
- Tubular
- Overflow
- Other
What is the pathogenesis of glomerular proteinuria?
- It is due to increased glomerular permeability to proteins.
- Can lead to nephrotic syndrome
- May be seen in all types of glomerulonephritis
- Protein loss tends to be more severe than in nonglomerular causes
What is the pathogenesis of tubular proteinuria?
Small proteins normally filtered at the glomerulus and then reabsorbed by the tubules appear in the urine because of abnormal tubules. This proteinuria is less severe than glomerular proteinuria.
What are some causes of tubular proteinuria?
- Sickle cell disease
- UTI
- interstitial nephritis
Example of overflow proteinuria
-Bence Jones Proteinuria due to Multiple Myeloma
What are other causes of proteinuria?
- UTI
- Fever
- Exertion/Stress
- CHF
- Pregnancy
- Orthostatic proteinuria
What are the 3 key features of nephrotic syndrome?
-Edema
-Proteinuria
-Hyperlipidemia
-Hypoalbuminemia
Other: hypercoagulable state, increased incidence of infection
What is the underlying cause of nephrotic syndrome?
-Significant glomerular disease resulting in abnormal glomerular permeability
Treatment for asymptomatic proteinuria?
If it is transient, no further workup is necessary. If it is persistent, further testing is indicated. Start by checking BP and examining urine sediment. Treat the underlying disease and associated problems.
Treatment for symptomatic proteinuria?
- Treat the underlying disease
- ACE inhibitors (decrease albumin loss)
- Diuretics
- Limit dietary protein and sodium
- Treat hypercholestolemia
- Vaccinate against flu and pneumococcus
Definition of hematuria?
> 3 RBCs/HPF on UA
Microscopic hematuria is more associated with?
Glomerular origin
Gross hematuria is more associated with?
Nonglomerular or urologic in origin
What should you consider when you see gross painless hematuria?
Bladder or kidney cancer until proven otherwise
What are some causes of hematuria
-Bladder or Kidney Cancer
-Infection
-Kidney stones
-Glomerular disease
-Trauma
-Strenuous exercise
-Systemic disease
-SCD
-Bleeding disorder
-Meds
-Polycystic kidney disease, simple cysts
-BPH
Just to name a few
What are the 4 common sites of obstruction by stones?
- ) Uterovesicular junction
- ) Calyx of the kidney
- ) Uteropelvic junction
- ) Intersection of the ureter and the iliac vessels
Risk factors for nephrolithiasis
- ) Low fluid intake
- ) Family history
- ) Conditions that precipitate stone formation: gout, Crohn’s, RTA type 1, hyperparathyroidism
- ) Medications: loops, acetazolamide, antacids, chemo)
- ) Male gender
- ) UTIs
- ) Dietary factors: low calcium and oxalate
What is the most common type of kidney stone?
Calcium: either oxalate or phosphate
What do calcium stones look like?
bipyramidal or biconcave ovals
Are calcium stones visible on a KUB?
Yes, they are radiodense