This unit is about the kidneys and the lungs. Module 11, Renal Disorders, covers what the kidney does and the labs that measure it, UTIs, nephrotic and nephritic syndrome, sudden kidney injury, long-term kidney disease, and other problems such as stones, PKD, bladder cancer, and loss of bladder control. Module 12, Respiratory, covers gas exchange and V/Q mismatch, COPD, asthma and other long-term lung disease, the sudden infections such as pneumonia, flu, and COVID, the emergencies such as ARDS, PE, and collapsed air sacs, and chest trauma. The exam has 50 questions, both multiple choice and select-all-that-apply.
The kidney filters your blood about 50 times a day. It also controls fluid, electrolytes, and pH. Start with the labs that measure it, and the infections that attack it.
| Test | What It Means |
|---|---|
| GFR | How much blood is filtered each minute. It is the main measure of kidney function. The GFR falls as the disease gets worse, and end-stage is under 15 mL/min/1.73 m². |
| Creatinine | A waste product from muscle breakdown that the kidney clears. As creatinine goes up, the GFR goes down. It is used to stage kidney disease. |
| BUN | Blood urea nitrogen, a waste product from protein breakdown. It rises as kidney function drops, and also with dehydration. |
| Lower UTI | Upper UTI |
|---|---|
| The bladder and urethra. The example is acute cystitis. You see sudden urges, going often, burning on urination, and discomfort low in the belly. | The kidney. The example is acute pyelonephritis. You see flank pain, fever, chills, and a patient who feels ill all over. It usually travels up from a lower UTI. |
Here are two glomerular syndromes that get mixed up every term. The difference comes down to one thing: what leaks out of the glomerulus.
| Nephrotic syndrome | Nephritic syndrome (AGN) | |
|---|---|---|
| Patho | The membrane turns leaky, but only to PROTEIN | Inflammation from immune complexes makes it leaky to everything: red cells, white cells, and protein |
| Main causes | Diabetes mellitus and lupus | An untreated strep infection, which gives post-streptococcal GN |
| Telltale signs | Over 3.5 g of protein a day, so the urine foams. The albumin drops, swelling appears around the eyes and in the arms and legs, and the blood lipids climb | Blood in the urine, which looks cola-colored, with red and white cells in the urine, plus high blood pressure, because sodium and fluid are held back |
Acute kidney injury (AKI) means kidney function drops suddenly, over hours to days. It is often reversible if you catch it early. Sort it by where the problem sits.
| Type | Problem | Causes |
|---|---|---|
| Pre-renal | Less blood reaching the kidney. The nephrons themselves start out healthy | Low blood volume from dehydration, bleeding, or shock. Also heart failure and atherosclerosis |
| Intra-renal | Damage inside the kidney itself | Acute tubular necrosis, glomerulonephritis, and drugs or dyes that harm the kidney, such as NSAIDs, IV contrast, and vancomycin |
| Post-renal | A blockage past the kidney, so pressure backs up | An enlarged prostate (BPH), a tumor, or stones. Urine backs up into the ureter and the kidney |
This is the most common cause inside the kidney. The tubule cells die, from poor blood flow or from toxins. They slough off and plug the tubules, so urine output drops and swelling follows.
| Phase | What Happens |
|---|---|
| 1. Oliguric | Under 400 mL in 24 hours. The BUN and creatinine rise, the patient is tired, and too much fluid can build up |
| 2. Diuretic | 2 to 4 L a day. Now the risk is dehydration, low volume, and low blood pressure. The BUN and creatinine level off |
| 3. Recovery | Urine output returns to normal, about 1 to 2 L a day. The GFR improves, and the BUN and creatinine fall |
Chronic kidney disease (CKD) means nephrons are lost for good, and the loss keeps going. The GFR falls, and fluid, waste, and electrolytes build up. It affects every system in the body.
The two most common causes are diabetes and high blood pressure.
| Goes UP (↑) | Goes DOWN (↓) |
|---|---|
| Creatinine and BUN, potassium, hydrogen ions, which means acidosis, and phosphate | GFR, calcium, vitamin D, and erythropoietin, which brings anemia |
Management: cut the sodium and potassium in the diet, avoid laxatives that contain magnesium, and give vitamin D and calcium. At end stage, with a GFR under 15 mL/min/1.73 m², the patient needs dialysis or a transplant.
These urologic problems come up often in practice, and on the exam.
| Disorder | Key Points |
|---|---|
| Nephrolithiasis (kidney stones) | Minerals get too concentrated and form crystals, and calcium is the most common one. Risks are a high calcium from an overactive parathyroid, a high uric acid, and not drinking enough. You see sudden severe flank pain that shoots toward the groin, vomiting, and sometimes blood in the urine. The pain starts when the stone moves from the kidney into the ureter. To prevent stones: drink plenty of water. |
| Polycystic kidney disease | This is inherited. Many cysts grow, swell the kidneys, and destroy working tissue. Early on there may be no symptoms. Later come flank pain, blood in the urine, getting up at night to urinate, and high blood pressure. You may even feel the kidneys. |
| Bladder cancer | Most of these are urothelial carcinoma. The classic sign is blood in the urine with no pain. It can look like a UTI at first. Smoking and chemical exposure raise the risk. |
| Urinary incontinence | Overflow means urine is held back by a blockage, as with an enlarged prostate. It is more common in men, and it raises the infection risk. Stress means the sphincter is weak, so urine leaks with a cough or a laugh. It is more common in women, and after pregnancies and with age. Urge, also called overactive bladder, means the bladder muscle squeezes on its own, which brings sudden strong urges. |
Breathing happens in three steps. Every lung disease breaks one of them. Name the broken step, and the symptoms follow.
| Step | What It Is | Diseases That Break It |
|---|---|---|
| Ventilation | Moving air in and out of the air sacs. These are obstructive problems | Asthma, COPD, OSA, cystic fibrosis, bronchitis |
| Diffusion | O₂ and CO₂ crossing the wall between the air sac and the capillary | Pulmonary edema, pneumonia, ARDS, emphysema |
| Perfusion | Blood flowing to the air sacs | Pulmonary embolism and pulmonary hypertension |
COPD means airflow is blocked, it gets worse over time, and it never fully reverses. It is an umbrella term that covers chronic bronchitis and emphysema, and many patients have both. The core trouble is getting air out.
| Chronic bronchitis | Emphysema | |
|---|---|---|
| Patho | Far too much mucus, plus inflamed airways, from a long-term irritant or toxin. It is not an infection | The air sacs are destroyed, and the lung loses its springiness. So the patient cannot breathe all the way out, and air gets trapped |
| Signs | A long-term wet cough, shortness of breath, low oxygen, and a high CO₂ | A barrel chest and a long, slow breath out, shortness of breath, and breathing through pursed lips |
In long-term COPD the CO₂ is often high all the time. Too much oxygen can push it higher. Here is why. Low oxygen makes the small blood vessels in the lung squeeze shut, which steers blood away from badly aired air sacs. Extra oxygen releases that squeeze. Blood then floods areas that get little air. So the match of air to blood flow gets worse, and more of each breath is wasted. Oxygen also pushes CO₂ off the hemoglobin. That is the Haldane effect. A small drop in the drive to breathe, the old hypoxic drive idea, adds a little on top. So give oxygen to a target saturation, 88 to 92 percent in COPD, not wide open, because too much oxygen can push the CO₂ to a dangerous level.
Here are the other long-term lung diseases: asthma, which can be reversed, plus the ones from work exposure, sleep, the blood vessels, and genes.
| Disease | Patho and Signs |
|---|---|
| Asthma | Two things go wrong at once: the airways tighten and they become inflamed, with mucus and swelling. It can be reversed. Signs: shortness of breath, a tight chest, wheezing, and a cough that is worse at night. Triggers include exercise and allergens |
| Cystic fibrosis | Autosomal recessive. The mucus is abnormally thick, which brings repeated lung infections, low oxygen, and poor growth |
| Pneumoconiosis ("black lung") | Breathing in dust, such as coal, silica, or asbestos, scars the lung. That blocks airflow and keeps the lung from expanding |
| Obstructive sleep apnea | The throat muscles relax and block the airway during sleep. Signs: tiredness during the day and trouble with memory. Risks are extra weight, being male, and alcohol. Over time it can cause pulmonary hypertension, which leads to right-sided heart failure |
| Pulmonary hypertension | The pressure in the pulmonary artery runs high, which strains the right ventricle and leads to right-sided heart failure. Other diseases can cause it, including COPD, PE, sleep apnea, and lung scarring |
Here are the sudden respiratory infections. They run from a mild chest cold to pneumonia in one lobe, plus the two big viruses.
Pharyngitis is a sore throat. Sinusitis brings face pain and congestion. Rhinitis is a runny nose. Laryngitis makes the voice hoarse. Treatment is usually comfort care.
| Condition | Patho and Signs |
|---|---|
| Acute bronchitis | It comes on fast and is usually viral, so people call it a chest cold. The bronchi are inflamed, there is a cough, and you often hear rhonchi. It clears on its own, so antibiotics are usually not needed |
| Pneumonia | It comes on fast and is usually bacterial, and it sits in one lobe. The air sacs fill with fluid. Signs: fever, a wet cough, crackles, low oxygen, shortness of breath, and confusion in older adults |
| Influenza | The virus attacks the lining cells of the airway. Signs: a high fever, body aches, headache, a dry cough, and a sore throat |
| COVID-19 | It attacks the lining cells of the air sacs, the type II pneumocytes, by latching onto the ACE-2 receptor. That inflames the deep lung, and the oxygen level can fall fast |
These are the sudden lung emergencies. They start fast, and patients go downhill fast.
| Condition | Patho and Signs |
|---|---|
| ARDS | Huge inflammation across both lungs makes the capillaries leaky, so the air sacs flood. Triggers: SEPSIS, burns, and trauma. Signs: hard shortness of breath, fast breathing, and an oxygen level that barely answers to oxygen |
| Pulmonary embolism | A clot breaks loose, usually from a DVT in the leg, and blocks a pulmonary artery. That creates dead space. Risks: a DVT, not moving, a broken femur, birth control pills, smoking, and extra weight. Signs: sudden shortness of breath, sharp chest pain with each breath, coughing up blood, and a low oxygen level |
| Atelectasis | The air sacs collapse. It happens when a small airway is blocked, or after surgery when breathing stays shallow. That part of the lung can no longer exchange gas |
Chest trauma breaks ventilation, and sometimes circulation too. Know the mechanics of each one.
| Injury | Patho and Signs |
|---|---|
| Flail chest | Several ribs break in more than one place each, so a loose piece of chest wall moves the wrong way. It pulls inward when the patient breathes in, and less air moves |
| Pneumothorax | Air gets into the space around the lung and pushes the two layers of pleura apart, so the lung collapses. Hemothorax means blood in that space instead of air |
| Tension pneumothorax | Trapped air keeps building up. It shoves the middle of the chest over and squeezes the heart and the great vessels. This is a MEDICAL EMERGENCY. Signs: low blood pressure, a fast heart rate, the trachea pushed AWAY from the bad side, bulging neck veins, and no breath sounds on one side |
| Easy to confuse | The key difference |
|---|---|
| Cystitis vs pyelonephritis | A lower UTI, in the bladder, with frequency and burning, versus an upper UTI, in the kidney, with flank pain and fever. |
| Nephrotic vs nephritic | A protein leak with swelling, from diabetes or lupus, versus inflammation with blood in the urine and high blood pressure, after strep. |
| Pre/intra/post-renal AKI | Less blood reaching the kidney / damage inside the kidney / a blockage past the kidney. |
| AKI vs CKD | Sudden and often reversible, versus permanent nephron loss that keeps getting worse. |
| Painful vs painless hematuria | Stones bring waves of pain. Bladder cancer brings no pain at all. |
| Shunt vs dead space | Blood with no air, versus air with no blood, as in a PE. |
| Chronic bronchitis vs emphysema | Mucus, cough, and a high CO₂, versus destroyed air sacs and a barrel chest. |
| Acute vs chronic bronchitis | Viral and clears on its own, versus a long-term irritant like smoking, as part of COPD. |
| Asthma vs COPD | Tight airways and inflammation that can be reversed, versus long-term blockage that never fully reverses. |
| Crackles vs wheezes vs rhonchi | Fluid, versus tight airways, versus mucus. |
| Pneumothorax vs tension pneumothorax | A collapsed lung in a stable patient, versus circulatory collapse, with the trachea pushed away, bulging neck veins, and low blood pressure. |
GFR: glomerular filtration rate, the main measure of kidney function. It falls as the disease gets worse.
Creatinine / BUN: waste markers that rise as kidney function drops.
Cystitis / Pyelonephritis: a bladder infection / a kidney infection.
Nephrotic syndrome: a glomerulus that leaks protein, which gives protein in the urine, a low albumin, swelling, and high blood lipids.
Nephritic syndrome: an inflamed glomerulus, which gives blood in the urine and high blood pressure. It often follows strep.
Acute tubular necrosis: the most common AKI from inside the kidney. The tubule cells die.
Hydronephrosis: a swollen kidney, because blocked urine has backed up into it.
CKD: chronic kidney disease, where nephrons are lost for good. Diabetes and high blood pressure are the usual causes.
Nephrolithiasis: kidney stones.
Ventilation / Diffusion / Perfusion: the three steps of breathing.
V/Q mismatch: air and blood flow no longer match, which gives a shunt or dead space.
Hypoxemia / Hypoxia: low oxygen in the blood / low oxygen in the tissues.
COPD: chronic obstructive pulmonary disease, which covers chronic bronchitis and emphysema.
Hypoxic drive: relying on a low oxygen level to trigger breathing. In long-term COPD it is only a small part of why extra oxygen raises the CO₂.
Pneumonia: an infection in one part of the lung that fills the air sacs with fluid.
ARDS: inflammation and flooding through the whole lung, with a low oxygen level that barely answers to treatment.
Pulmonary embolism: a clot blocking a pulmonary artery, which makes dead space.
Atelectasis: collapsed air sacs, often after surgery.
Tension pneumothorax: trapped air around the lung squeezing the heart. It is an emergency.