Step Up - Diseases of the Renal and Genitourinary System Flashcards
AKI is also called?
ARF - Acute renal failure.
Types of AKI:
Prerenal - Decrease in renal blood flow (60-70% of cases).
Intrinsic - Damage to renal parenchyma (25-40% of cases).
Postrenal - Urinary tract obstruction (5-10% of cases).
AKI is oliguric, anuric, or nonoliguric?
It can be either. Severe AKI may occur without a reduction of urine output.
Most common clinical findings in patients with AKI?
Weight gain + edema - This is due to a positive water and Na balance.
AKI is characterized by?
Azotemia - elevated BUN + Cr.
Elevated BUN is also seen with?
Catabolic drugs (eg steroids), GI/soft tissue bleeding, and dietary protein intake.
Elevated Cr is also seen with?
Incr. muscle breakdown and various drugs. Baseline Cr level varies proporptionately with muscle mass.
Prognosis of AKI:
> 80% recover completely. However, the prognosis varies widely depending on the severity of renal failure and the presence of comorbid conditions.
MCC of death in AKI?
Infection - 75%. Followed by cardiorespiratory complications.
MCC of AKI?
Prerenal failure - potentially reversible.
What drugs should NOT be given in patients with decr. renal perfusion?
- NSAIDs (constrict afferent arteriole).
- ACEIs (vasodilate efferent arteriole).
- Cyclosporin.
ALL can precipitate prerenal failure.
Monitoring a patient with AKI:
- Daily weights, intake, and output.
- BP.
- Serum electrolytes.
- Watch Hb and Hct for anemia.
- Watch for infection.
Diagnostic approach in AKI:
- History + Physical exam.
- 1st thing to do is to determine the DURATION of renal failure –> Baseline Cr.
- 2nd thing is to determine whether AKI is due to prerenal, intrarenal, and postrenal causes –> Combine history, physical exam, lab findings.
- Medication review.
- Urinanalysis.
- Urine chemistry (FENa, osmolarity, urine Na, urine Cr).
- Renal US - To rule out obstruction.
Prerenal vs ATN - Urine osmolarity:
Prerenal - >500.
ATN - >350.
Prerenal vs ATN - Urine Na:
Prerenal: 40.
Prerenal vs ATN - FENa:
Prerenal: 1%.
Prerenal vs ATN - Urine sediment:
Prerenal: Scant.
ATN: Full, brownish pigment, granular casts with epithelial casts.
Studies to differentiate prerenal from intrinsic AKI - Urinanalysis:
Prerenal: Hyaline casts.
Intrinsic: Abnormal.
Studies to differentiate prerenal from renal AKI - BUN/Cr:
Prerenal –> >20:1.
Renal –> <20:1.
Studies to differentiate prerenal from renal AKI - FENa:
Prerenal –> >2-3%.
Studies to differentiate prerenal from renal AKI - Urine osmolarity:
Prerenal: >500mOsm.
Renal: 250-300mOsm.
Studies to differentiate prerenal from renal AKI - Urine sodium:
Prerenal –> >40.
Prerenal failure - Why Oliguria ALWAYS?
To preserve volume.
Prerenal failure - Why BUN-to-serum Cr >20:1?
Because kidneys can reabsorb urea.
Prerenal failure - Incr. urine osmolarity?
> 500, because the kidneys are able to reabsorb water.
Prerenal failure - Decr. urine Na?
Because Na is avidly reabsorbed.
Prerenal failure - Incr. urine-plasma Cr ratio (>40:1)?
Because much of the filtrate is reabsorbed (but not the Cr.).
MCC of ATN?
Ischemia.
Rhabdomyolysis - Etiology:
Caused by trauma, crush injuries, prolonged immobility, seizures, snake bites.
Rhabdomyolysis - Problem with the kidneys?
Release of muscle fibers contents (myoglobin) into bloodstream –> Toxic to the kidneys, which can lead to AKI.
Rhabdomyolysis - Lab:
- Include markedly elevated CPK.
- Hyperkalemia.
- Hypocalcemia.
- Hyperuricemia.
Rhabdomyolysis - Treatment:
- IV fluids.
- Mannitol (osmotic diuretic).
- Bicarbonate (drives K back into cells).
ATN in multiple myeloma?
From kappa and lamda light chains.
Intrinsic renal failure - BUN/Cr closer to 10:1?
Both are still elevated, but LESS UREA IS REABSORBED than in prerenal failure.
Intrinsic renal failure - Incr. urine Na (FENa >2%-3%)?
Na is poorly reabsorbed.
Intrinsic renal failure - Decr. urine osmolarity (<350)?
Because renal water reabsorption is impaired.
Intrinsic renal failure - Decr. urine-plasma Cr ratio (<20:1)?
Because filtrate cannot be reabsorbed.
Least common cause of AKI?
Postrenal failure.
Post renal failure - What is essential to take place for Cr to rise?
BOTH kidneys must be obstructed for Cr to rise.
Post renal obstruction if untreated, can lead to?
ATN
Post renal failure - etiology:
- Urethral obstruction secondary to BPH - MCC.
- Obstruction of solitary kidney.
- Nephrolithiasis.
- Obstructing neoplasm (bladder, cervix, prostate, and so on).
- Retroperitoneal fibrosis.
- Ureteral obstruction is an uncommon cause, because it needs to be bilateral.
3 basic tests for post renal failure:
- Physical exam –> Palpate the bladder.
- US –> Look for obstruction, hydronephrosis.
- Catheter –> Look for large volume of urine.
How is diagnosis of AKI usually made?
By finding elevated Cr and BUN. Patient is usually ASYMPTOMATIC.
Course of ATN:
- Onset (insult).
- Oliguric phase.
- Diuretic phase.
- Recovery phase.
Oliguric phase of ATN:
- Azotemia and uremia - 10-14d.
2. Urine output <400-500mL/d.
Diuretic phase of ATN:
- Begins when urine output is >500mL/d.
- High urine output due to the following:
a. Fluid overload (excretion of retained salt, water, other solutes that were retained during oliguric phase).
b. Osmotic diuresis due to retained solutes during oliguric phase.
c. Tubular cell damage - delayed recovery of epithelial cell function relative to GFR.
Obtain the following in any patient with AKI:
- Urinanalysis.
- Urine chemistry.
- Serum electrolytes.
- CBC.
- Bladder catheterization to rule out obstruction - diagn. + therapeut.
- Renal US to look for obstruction.
Microscopic exam of the urine sediment - Hyaline casts:
Devoid of contents - seen in prerenal failure.
Microscopic exam of the urine sediment - RBC and WBC casts:
RBC casts –> Glomerular disease.
WBC casts –> Renal parenchymal infl.
Microscopic exam of the urine sediment - Fatty casts:
Nephrotic syndrome.
ATN - Urine sediment:
- Muddy brown casts.
- Renal tubular cells/casts.
- Granular casts.
ATN - Protein and blood in urine?
Protein –> Trace.
Blood –> No.
Acute GN - Urine sediment:
- Dysmorphic RBCs.
- RBCs with casts.
- WBCs with casts.
- Fatty casts.
Acute GN - Protein and blood:
Protein –> 4+.
Blood –> 3+.
Acute interstitial nephritis - Urine sediment:
- RBCs.
- WBCs.
- WBCs with casts.
- Eosinophils.
Acute interstitial nephritis - Protein and blood:
Protein –> 1+.
Blood –> 2+.
Post renal - urine sediment:
- Benign.
- May or may not see RBCs.
- WBCs.
Post renal - Protein and blood:
Protein –> No.
Blood –> No.
Urine Na depends on?
Dietary intake.
FENa:
Prerenal.
2-3% –> ATN.
When FENa is most useful:
If OLIGURIA is present.
What is the renal failure index 5?
UNa/(UCr/UpCr) x 100.
Prerenal failure.
>1% –> ATN.
CT scan role in diagnosis of AKI:
CT abdomen and pelvis - may be helpful - usually done if US shows an abnormality, such as hydronephrosis.
Renal biopsy in diagnosis of AKI:
Usually done if there is suspicion of acute GN or acute allergic interstitial nephritis.
Renal arteriography in diagnosis of AKI:
For possible renal artery occlusion - should be performed only if specific therapy will make a difference.
What types of AKI should be excluded first in the course of diagnosis?
In evaluating a patient with AKI, first exclude PRE- and POST-renal causes, and then, if necessary, investigate intrinsic renal causes.
In the EARLY phase of AKI, the MC mortal complications are:
- Hyperkalemic cardiac arrest.
2. Pulmonary edema.
AKI - Why hyperkalemia?
Due to:
- Decr. excretion of K.
- Movement of K from ICF to ECF due to tissue destruction and acidosis.
AKI - Why metabolic acidosis with incr. anion gap?
Due to:
1. Decr. excretion of H.
If severe (<16mEq/L), correct with HCO3.
AKI - Hypocalcemia?
Loss of ability to form active vitD + rapid development of PTH resistance.
AKI - Hyponatremia?
May occur if water intake is greater than body losses, or if a volume-depleted patient consumes excessive hypotonic solutions.
HYPERnatremia may also be seen in hypovolemic states.
AKI - Hyper- or Hypophosphatemia?
HYPER
AKI - Infection?
A COMMON + SERIOUS complication - 50-60% of cases.
Cause –> Multifactorial, but UREMIA is thought to impair immune functions.
AKI - Treatment - General measures:
- Avoid medications that decr. RBF (NSAIDs) and/or are nephrotoxic (aminoglycosides, radiocontrast agents).
- Adjust medication dosages for level of renal function.
- Correct fluid imbalance.
- Correct electrolyte disturbances if present.
- Optimize CO. BP should be 120-140/80-90.
AKI - Treatment - When to order dialysis:
- If symptomatic uremia.
- Intractable acidemia.
- Hyperkalemia.
- Volume overload
Radiographic contrast media can cause?
ATN –> Typically very rapidly, by causing spasm of the afferent arteriole.
It can be prevented with saline hydration.
Whenever a patient has elevated Cr levels, the 1st thing to do is?
Determine the patient’s BASELINE Cr levels, if possible.
This helps determine whether the patient has AKI, CKD, or chronic renal insufficiency/failure with superimposed AKI (“acute on chronic” renal failure).
CKD is defined:
As either decr. kidney function (GFR<60) or kidney damage (structural/functional abnormalities) for AT LEAST 3 MONTHS regardless of cause.
CKD - Etiology:
- DM - MCC (30%).
- HTN - 25%.
- Chronic GN - 15%.
- Interstitial nephritis.
- PKD.
- Obstructive uropathy.
Azotemia refers?
To elevated BUN.
Uremia refers?
To the signs and symptoms associated with accumulation of nitrogenous wastes due to impaired renal function.
Difficult to predict when uremic symptoms will appear, but it rarely occurs unless the BUN is >60mg/dL.
ESRD is defined?
It is a loss of kidney function that leads to lab and clinical findings of uremia.
It is NOT defined by BUN and Cr levels.
CKD - Clinical features - CVS:
- HTN
- CHF
- Pericarditis (uremic)
CKD - Clinical features - GI:
Usually due to uremia:
- Nausea, vomiting.
- Loss of appetite (anorexia).
CKD - Clinical features - Neurologic:
- Lethargy, confusion, peripheral neuropathy, uremic seizures.
- Weakness, asterixis, hyperreflexia.
- Hypocalcemia –> lethargy, confusion, tetany.
CKD - Clinical features - Hematologic:
- Normocytic normochromic anemia - may be severe.
2. Bleeding secondary to platelet dysfunction - due to uremia. - Platelets do NOT degranulate in a uremic environment.
CKD - Clinical features - Endocrine/metabolic:
- Ca-Ph disturbances –> Hyper Ph –> Decr. renal prod. of vitD –> HypoCa –> 2o HyperPTH.
- In the long run –> HYPERcalcemia may be seen.
- Sexual/reproductive symptoms.
- Pruritus - Common and difficult to treat.
Renal osteodystrophy?
Hypocalcemia leads to secondary hyperPTH, which removes Ca from the bones, making them weak and susceptible to fracture.
CKD - Clinical features - Fluid and electrolyte problems:
- Volume overload - watch for pulm. edema.
- HyperK - decr. secretion.
- HyperMg - 2o to reduced urinary loss.
- HyperPh.
- Met. acidosis - due to loss of renal mass (thus decr. ammonia production) and the kidney’s inability to excrete H.
CKD - Clinical features - Immunologic:
Uremia –> Inhibits cellular and humoral immunity.
Diagnosis of CKD:
- Urinanalysis - Examine sediment.
- Measure Cr clearance to estimate GFR.
- CBC - Anemia, thrombocytopenia.
- Serum electrolytes.
- Renal US - Evaluate SIZE of kidneys/rule out obstruction.
Does presence of normal or large sized kidneys exclude CKD?
No.
In patients with CKD, the MC complications that require urgent intervention are?
- Symptomatic volume overload.
2. Severe hyperkalemia.
Life-threatening complications in CKD:
- Hyperkalemia –> Obtain an ECG.
- Pulmonary edema –> Look for recent weight gain.
- Infection.
CKD Treatment - Diet:
- Low protein.
- Low salt diet if HTN, CHF, or oliguria are present.
- Restrict K, Ph, Mg intake.
CKD Treatment - ACEIs:
Dilate efferent arteriole of glomerulus:
- If used early on, they reduce the risk of progression to ESRD because they slow the progression of proteinuria.
- Use with great caution because they can cause HYPERKALEMIA.
CKD Treatment - BP control:
- Strict control decreases the rate of disease progression.
2. ACEIs are the preferred agents. Diuretics may be required.
CKD Treatment - Correction of electrolytes:
- Correct hyperPh –> With Ca citrate (a phosphate binder).
- Long term Ca + vitD –> Prevent 2o hyperPTH and uremic osteodystrophy.
- Acidosis –> Treat the underlying cause (renal failure) - Patients may require oral HCO3.
CKD Treatment - Pruritus:
Try capsaicin cream or cholestyramine and UV light.
CKD Treatment - What is the only cure?
Transplantation
2 major methods of dialyzing a patient:
- Hemodialysis
2. Peritoneal dialysis
Settings in which dialysis is considered:
- CKD.
- AKI.
- Overdose of medications or ingestions of substances cleared by the kidneys.
Absolute indications for dialysis:
- Acidosis
- Electrolytes - Severe hyperkalemia.
- Intoxications - methanol, ethylene glycol.
- Overload - hypovolemia not managed by other means.
- Uremia (severe) - based on clinical presentation, not lab values - eg uremic pericarditis.
Specific indications for dialysis - Nonemergent indications:
- Cr and BUN are NOT absolute indications for dialysis.
- Symptoms of uremia:
a. Nausea, vomiting.
b. Lethargy/deterioration in mental status.
c. Encephalopathy.
d. Seizures.
e. Pericarditis.
Specific indications for dialysis - Emergent indications:
- Life-threatening manifestations of volume overload - Pulm. edema, HTN emergency.
- Severe, refractory electrolyte disturbances.
- Severe metabolic acidosis.
- Drug toxicity/ingestions.
Dialyzable substances:
- Salicylic acid
- Lithium
- Ethylene glycol
- Mg-containing laxatives
Frequency for hemodialysis:
Most hemodialysis patients require 3-5hrs of dialysis 3days/week.
Limitations of dialysis:
Dialysis does NOT replicate the kidney’s synthetic functions –> EPO, vitD deficiency.
Complications associated with hemodialysis:
- Hypotension
- Relative hypo-osmolarity of the ECF compared with the brain may result in nausea, vomiting, headache, and rarely, seizures or coma.
- “1st use syndrome”.
- Complications with the anticoagulation.
- Infections of vascular sites –> sepsis.
Proteinuria - Definition:
Urinary excretion of >150mg protein /24h.
Asymptomatic TRANSIENT proteinuria:
Has an EXCELLENT prognosis - NO further evaluation is required.
Asymptomatic PERSISTENT proteinuria + Symptomatic proteinuria:
Require further work-up - high chance of renal disease in these patients.