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Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Acute Kidney Injury

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In one line

·The kidneys suddenly stop cleaning the blood fast enough—waste piles up, salt and water go out of balance, and every organ starts to feel it within hours to days.

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Normal physiology

·Each kidney holds about one million tiny filters called nephrons. Blood flows into each nephron under high pressure. Water and small molecules—waste, sugar, salt—squeeze out of the blood into a collecting cup called Bowman's capsule. Then a long, twisting tube pulls back the useful stuff (water, sodium, glucose) and leaves behind the waste (creatinine, urea, extra potassium). What is left becomes urine. The kidneys also make two important hormones: erythropoietin (EPO), which tells your bone marrow to make red blood cells, and renin, which helps control blood pressure. They also turn on vitamin D so your bones can use calcium.

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What goes wrong

·Something suddenly stops the kidney from doing its job. There are three big ways this happens. Pre-renal means not enough blood is reaching the kidney—picture a garden hose kinked so no water flows through. This happens with dehydration, severe bleeding, heart failure, or shock. Intrinsic-renal (also called intrinsic AKI) means the filter tissue itself gets damaged—like the filter screen gets torn or clogged. The most common cause is acute tubular tissue death (necrosis), or ATN, where the tubule cells die from lack of oxygen or are poisoned by drugs (aminoglycoside antibiotics, NSAIDs like ibuprofen, or IV contrast dye used in CT scans). Post-renal means the drain is blocked downstream—a kidney stone stuck in the ureter, an enlarged prostate squeezing the urethra, or a bladder tumor. Pressure backs up into the kidney and crushes the filters from the inside.

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Hallmark signs

·Decreased urine output (oliguria < 400 mL/day or no urine output (anuria) < 100 mL/day)
·Swelling in legs, ankles, hands, or face (peripheral swelling (edema))
·Shortness of breath, wet cough, or crackles on lung exam (pulmonary swelling (edema))
·Nausea, vomiting, and loss of appetite
·Itching all over (uremic itching (pruritus))
·Confusion, drowsiness, or altered mental status (uremic encephalopathy)
·Fatigue and muscle weakness
·Full, swollen bladder you can feel in the lower belly (suprapubic fullness)

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Red flags · escalate now

·Potassium > 6.5 mEq/L or EKG changes (peaked T waves, wide QRS, sine wave)—heart can stop at any moment (cardiac arrest)
·Pulmonary edema (fluid flooding the lungs) (wet lungs, crackles, shortness of breath) not getting better with diuretics (water pills like furosemide)—dialysis needed urgently to pull fluid off
·Uremic encephalopathy (confusion, lethargy), pericarditis (chest pain with friction rub), or uremic bleeding (nose bleeds, bruising)—severe severe waste buildup in the blood (uremia) requiring urgent dialysis
·No urine output (Anuria) (no urine at all) plus a palpable bladder or hydronephrosis (swollen kidneys) on ultrasound—obstruction blocking urine flow; needs urgent catheter or nephrostomy tube
·Toxic ingestion (methanol, ethylene glycol, lithium, aspirin overdose)—dialyzable poison requiring emergent hemodialysis to remove it before it kills the patient

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Workup

·Serum creatinine and blood urea nitrogen (BUN), compared to the patient's usual baseline
·Urinalysis with microscopy (looking at the urine under a microscope)
·Urine sodium and fractional excretion of sodium (FENa)
·Renal ultrasound (sound-wave pictures of the kidneys)
·Electrolyte panel (blood test for potassium, bicarbonate, phosphate, calcium)
·Electrocardiogram (EKG, heart tracing) if potassium is high or the patient has chest pain, palpitations, or weakness
·Complete blood count (CBC) with differential
·Creatine kinase (CK) if rhabdomyolysis (muscle breakdown) is suspected (history of trauma, seizure, prolonged immobility, or drug use)

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Treatment

·Stop all nephrotoxic drugs immediately: NSAIDs (ibuprofen, naproxen, ketorolac), aminoglycoside antibiotics (gentamicin, tobramycin), hold ACE inhibitors or ARBs, hold metformin
·Give intravenous isotonic crystalloid fluids (normal saline or lactated Ringer's solution) ONLY if the patient is volume-depleted (dry mucous membranes, low blood pressure, high heart rate)
·Give loop diuretics (furosemide, bumetanide) if the patient is fluid-overloaded with crackles in the lungs or swelling—do NOT use in pre-renal AKI
·Treat high potassium (hyperkalemia) in the following sequence: (1) intravenous calcium gluconate 1 gram over 2 to 3 minutes, (2) insulin 10 units IV with dextrose 25 grams IV, (3) inhaled albuterol 10 to 20 mg by nebulizer, (4) oral or rectal potassium binders (sodium polystyrene sulfonate, patiromer, sodium zirconium cyclosilicate), (5) urgent dialysis if refractory
·Relieve urinary obstruction urgently: place a Foley catheter if the bladder is blocked (urinary retention), place a nephrostomy tube (tube through the skin into the kidney) or ureteral stent (tube inside the ureter) if the ureters or kidney outlet are blocked
·Start renal replacement therapy (hemodialysis or continuous renal replacement therapy, CRRT) using the mnemonic AEIOU: Too much acid in the blood (Acidosis) (pH less than 7.1 that does not respond to bicarbonate), Electrolytes (hyperkalemia refractory to medical treatment), Ingestions (toxic alcohols like ethylene glycol or methanol, lithium), fluid Overload (pulmonary swelling (edema) not responding to diuretics), Severe waste buildup in the blood (Uremia) (encephalopathy, pericarditis, or bleeding from platelet dysfunction)
·Adjust all medication doses for reduced kidney function using the calculated glomerular filtration rate (GFR or eGFR); avoid contrast dye unless absolutely necessary, and if needed, give intravenous isotonic saline before and after contrast to reduce risk

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NCLEX trap

·Furosemide does not fix pre-renal AKI (kidney injury caused by too little blood flowing to the kidneys)—it actually makes dehydration worse and harms the kidneys more. First, give IV fluids to fill the blood vessels back up, and stop any medicines that can poison the kidneys (like NSAIDs or aminoglycosides).
·Stop metformin right away. When the kidneys fail, metformin piles up in the blood and causes lactic acidosis (acid from oxygen-starved tissues) (a dangerous buildup of lactic acid that can kill). Only restart metformin after the kidneys are stable and the eGFR (a score that tells how well kidneys filter blood) is above 30.
·Calcium does NOT lower potassium. It protects the heart from stopping when potassium is dangerously high. To actually lower potassium, give insulin plus sugar (shifts potassium into cells), albuterol breathing treatment (also shifts potassium in), or medicines like Kayexalate, patiromer, or Lokelma (remove potassium from the body). If those don't work fast enough, dialysis is needed.
·Most AKI gets better with IV fluids, fixing the cause, and stopping kidney-toxic drugs. Dialysis is only needed if AEIOU criteria show up: Too much acid in the blood (Acidosis) (blood pH under 7.1 that won't respond to treatment), Electrolytes (potassium over 6.5 that won't come down), Ingestion (poison that dialysis can remove), Overload (fluid in the lungs that diuretics can't fix), Severe waste buildup in the blood (Uremia) (kidney waste so high it causes heart sac inflammation, brain confusion, or bleeding).
·Low urine can mean the kidneys are failing, OR it can mean the bladder is blocked (like from a big prostate or a kinked catheter). Always check for obstruction first—put in a catheter or do an ultrasound to see if urine is trapped. If the bladder empties and there's little urine inside, then the kidneys truly aren't making enough urine.

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