An adult passes 1 to 2 litres of urine a day without a second thought, until something blocks or infects the tract. Two disorders top the exam list: infections and stones. Learn the cause, the signs and the treatment for each, and the stone types by their chemistry.
Chapter 14 of the PECTAA Biology 12 book is the Human Urinary System. Section 14.3 covers disorders of the urinary tract, starting with urinary tract infections (14.3.1) and kidney stones (14.3.2). This note is for FSc Part 2 (2nd year, Class 12) students in Lahore, Faisalabad, Sargodha, Rawalpindi, Multan, Gujranwala and the other Punjab boards. Gujrat district comes under the Gujranwala board. PECTAA writes the books. Your own board sets your paper.
What to know
Disorders of the urinary tract. The book lists urinary tract infections, kidney stones, kidney failure and polycystic kidney disease as common disorders. This note covers the first two.
1. Urinary tract infections (UTIs).
- Cause: usually bacteria, most commonly Escherichia coli. They enter through the urethra and infect the bladder, ureters or kidneys.
- Symptoms: a frequent and urgent need to pass urine, pain or burning while urinating, cloudy or strong-smelling urine, lower abdominal pain, and sometimes fever or chills.
- Treatment: a course of antibiotics to kill the bacteria. Drinking plenty of water and urinating often help flush the bacteria out and ease symptoms.
2. Kidney stones. Hard, crystalline mineral material that sticks together into small "pebbles" in the kidney or urinary tract. They may stay in the kidney or pass out through the tract.
Types of stones and their causes.
- Calcium oxalate (about 70% of patients): linked to hypercalciuria (high calcium in urine) and hyperoxaluria (high oxalate in urine).
- Uric acid (about 10% of patients): linked to hyperuricemia (high uric acid in blood).
- Others: high levels of cystine and phosphates in urine also cause stones.
- Risk factor: continued dehydration raises the chance of stone formation.
Urine chemistry clue (book side note). Doctors study a patient's urine to judge the stone type. In acidic urine the stone tends to be calcium oxalate; when urine stays persistently acidic, uric acid stones form; in alkaline urine the stone is calcium phosphate.
Treatment: lithotripsy, meaning breaking the stone. Two methods:
- Extracorporeal shockwave lithotripsy (ECSWL). A machine called a lithotripter sends shockwaves from outside the body. The stone breaks into small pieces, most of which pass out in the urine.
- Percutaneous nephrolithotripsy (PNL). Used for larger stones. A tube is inserted from the patient's back into the kidney. A small camera, the nephroscope, shows the stone. Ultrasound equipment breaks it, and the pieces are grasped and pulled out.
The two methods side by side.
| Feature | ECSWL | PNL |
|---|---|---|
| Full name | Extracorporeal shockwave lithotripsy | Percutaneous nephrolithotripsy |
| Where it works from | outside the body | a tube through the back into the kidney |
| What breaks the stone | shockwaves from a lithotripter | ultrasound equipment |
| How pieces leave | mostly pass out in urine | grasped and pulled out |
| Used for | stones that shockwaves can break up | larger stones |
Linking the two disorders to water. Drinking plenty of water helps flush bacteria in a UTI, and the book names continued dehydration as a cause that raises the chance of stones. In both cases, a steady flow of dilute urine works against the problem.
Key points
- UTI = bacteria (usually E. coli) → antibiotics.
- Stones = minerals → lithotripsy. Calcium oxalate is the most common.
- ECSWL works from outside; PNL goes in through the back for large stones.
Worked examples
Example 1. A patient has burning urination, cloudy urine and mild fever. What is the likely disorder and treatment? A urinary tract infection. Treatment is a course of antibiotics, with plenty of water.
Example 2. Out of 200 kidney stone patients, about how many would have calcium oxalate stones, using the book's figure? 70% of 200 = 140 patients.
Example 3. Out of the same 200, about how many would have uric acid stones? 10% of 200 = 20 patients.
Example 4. Why might a doctor choose PNL over ECSWL? The stone is large. PNL reaches the stone directly through a tube in the back, breaks it and removes the pieces.
Common mistakes in the exam
- Saying UTIs are caused by viruses. The book names bacteria, most commonly E. coli.
- Mixing hypercalciuria and hyperuricemia. The first is calcium in urine; the second is uric acid in blood.
- Calling ECSWL surgery through the skin. ECSWL is from outside the body; PNL uses a tube into the kidney.
- Forgetting dehydration as a risk factor for stones.
- Mixing "cysteine" and "cystine". The stone-forming substance is cystine.
Exam technique
- For each disorder write cause, symptoms and treatment as three labelled lines.
- Name both lithotripsy methods in full before using the short forms.
- Quote the book's percentages (70% and 10%) when asked about stone types.
- Check your board's notice for the topics in your paper.
Practice questions
Which bacterium most commonly causes UTIs? Answer: Escherichia coli.
What is hyperoxaluria? Answer: An increased level of oxalate in urine.
Name the instrument that produces shockwaves in ECSWL. Answer: The lithotripter.
What is the camera used in PNL called? Answer: The nephroscope.
In alkaline urine, which type of stone forms? Answer: Calcium phosphate.
Name the four common urinary tract disorders listed in the book. Answer: Urinary tract infections, kidney stones, kidney failure and polycystic kidney disease.
Which condition is high uric acid in the blood, and which stone does it cause? Answer: Hyperuricemia; uric acid stones.
Ready to practise this? Continue in 2nd Year Biology.