Renal Tract Flashcards
What is a urinary tract infection?
Infection of bladder (cystitis).
What is the most common pathogen causing UTIs?
E. coli
How does E. coli cause a UTI?
Transurethral ascent of colonic commensals (E. coli)
UTIs are normally uncomplicated and resolve within a few days.
Give some risk factors for uncomplicated UTIs?
- Female
- Sexual activity
- Certain types of birth control; diaphragms, spermicidal agents
- Menopause
- Diabetes mellitus
Why are females more prone to UTIs?
Shorter urethra
Why can menopause predispose to UTIs?
Decline in circulating oestrogens in menopause causes changes in urinary tract that make you more vulnerable to infection (e.g. vaginal atrophy)
UTIs can be complicated. Give some situations that cause a UTI to be complicated
- Pregnancy
- Urinary catheterisation
- Comorbidities e.g. immunosuppression
- Atypical/resistant organisms
- Structural/neurological abnormalities
- 3 months post-renal transplant
What complication can a UTI lead to in pregnancy?
Pre-term delivery and low birthweight
Give some complications of UTIs
- Pyelonephritis
- Urosepsis
- Impaired renal function
What symptoms are typically seen in UTIs?
- Urgency
- Frequency
- Dysuria (pain)
- Suprapubic tenderness
- Foul-smelling urine
- Change in urine appearance
In those with underlying cognitive impairment, typical features of UTIs may be absent. How may they present?
with delirium and reduced functional ability
Aside from an abdo exam, what other exam may be helpful in the context of a potential UTI?
Genital examination if vulvovaginal atrophy or herpes simplex is possible
What is the main sign typically seen in UTIs?
Suprapubic tenderness during palpation
What is the main investigation in UTIs?
Urine dipstick
What would a urine dipstick typically show in UTIs?
Positive for leucocytes and nitrites in most cases
Mid stream urine samples should only be sent in which patient populations in a potential UTI?
- High-risk groups (e.g. pregnancy)
- Men
- Children
- Recurrent UTIs
Typical results of a MSU in a UTI?
+ve for nitrites or leukocytes and RBCs → UTI likely
If the MSU is negative for nitrites, leukocytes and RBCs in the context of a potential UTI, what does this indicate?
UTI less likely
Who is a urine dipstick unreliable in?
- Women >65 y/o
- Catheterised patients
What are the red flags in a UTI?
- Haematuria
- Loin & groin pain
- N&V
- Fever
- Rigors
- Change in mental state
What PMH should you ensure to ask about when assessing a patient with potential UTI
- Possible pregnancy → get test!
- Diabetes mellitus
- Neurological conditions
- Immunosuppression
- Urolithiasis
- Bladder catheterisation
What is the typical treatment for uncomplicated UTIs?
Conservative:
- Fluid intake
- Post-coital voiding
- Analgesia
How should you safety net in the context of a UTI?
Any signs of fever, haematuria, loin pain, N&V, altered mental state → seek medical attention
What is the 1st choice Abx in acute, uncomplicated UTIs?
Nitrofurantoin
What is an alternative to nitrofurantoin in UTIs?
Trimethoprim, amoxicillin, cephalexin
Spectrum of nitrofurantoin?
Active against most organisms that cause uncomplicated UTIs including E. coli (gram-negative) and Staph. saprophyticus (gram-positive)
Is E. coli gram positive or negative?
Negative
Mechanism of nitrofurantoin?
- Metabolised in bacterial cells by nitrofuran reductase
- Its active metabolite damages bacterial DNA and causes cell death (bactericidal)
Which type of bacteria are resistant to nitrofurantoin?
Bacteria with lower nitrofuran reductase activity are resistant to nitrofurantoin (rare for E. coli)
How can nitrofurantoin affect urine colour?
Nitrofurantoin specifically can turn urine dark yellow or brown
Side effects of nitrofurantoin?
- GI upset – nausea, diarrhoea
- Immediate & delayed hypersensitivity reactions
- Nitrofurantoin specifically can turn urine dark yellow or brown
What side effect may occur with the use of nitrofurantoin in neonates?
haemolytic anaemia
Contraindications for nitrofurantoin?
- Pregnancy towards term (avoid in 3rd trimester)
- Babies in first 3 months of life
- Renal impairment → leads to impaired excretion, increased toxicity, and reduced efficacy
- Long term use for chronic UTIs → increases risk of adverse effects (particularly in elderly)
Why is nitrofurantoin contraindicated in renal impairment?
Eliminated via kidneys → leads to impaired excretion, increased toxicity, and reduced efficacy
How should pregnant women with asymptomatic bacteriuria** and/or **suspected/proven UTI be treated?
Treat with antibiotic course (and followed up) → be careful of which trimester!!!
Which trimester is trimethoprim advised against in? Why?
1st → folate antagonist
Which trimester is nitrofurantoin advised against in? Why?
3rd → due to risk of haemolytic anaemia
Antenatal services should be informed if which pathogen is identified in the urine of a pregnant women?
group B streptococcal bacteriuria
What is the key differential of a UTI?
Pyelonephritis (UTI affecting the kidneys)
How would pyelonephritis present that could distinguish it from UTI?
Urinary symptoms +
- Febrile (pyrexia)
- Vomiting
- Loin & groin pain
- Renal angle tenderness
If haematuria persists following the treatment of a UTI, what may this indicate?
Possible underlying malignancy
Bladder cancer can also present with; haematuria, irritation or pain when urinating, dysuria etc
Mechanism of disease in pyelonephritis?
Usually bacteria travelling up from bladder (transurethral ascent of colonic commensals, usually E.coli)
Most common pathogen causes pyelonephritis?
E. coli
If catheter present or abnormal renal tract, what pathogen is more likely to cause pyelonephritis?
E. coli or Pseudomonas aeruginosa
How is a diagnosis of pyelonephritis made?
- UTI symptoms + loin pain/fever
- Culturing urinary pathogen
Main complication of pyelonephritis to worry about?
Sepsis - tachycardia, hypotension, SOB, sweating, rigors, pallor
Risk factors for pyelonephritis?
- Pregnancy
- Diabetes
- Structural renal abnormalities
- Immunocompromised
What is the key differential for pyelonephritis? How can you tell them apart?
Cystitis → key differential (lower UTI)
- Rarely pyrexial
- Rarely loin/flank tenderness
Prognosis of pyelonephritis?
- Usually responds well to antibiotic therapy – time to resolution of symptoms depends largely on initial severity of disease (complete and uncomplicated recovery within days to weeks).
- Prognosis less favourable in older people and those with complicating factors (e.g. immunosuppressed)
What important bedside investigations should you do in pyelonephritis?
- Urine dipstick
- Pregnancy test
Typical results of urine dipstick in pyelonephritis?
typically positive for leucocytes and nitrites
What bloods would you get in pyelonephritis?
- FBC (raised WCC)
- U&Es (check renal function)
- Blood cultures (before Abx)
What other test should you send to lab in pyelonephritis?
Urine MSU for MC&S → obtain sample before starting empirical drug treatment
Immediate management of pyelonephritis?
Admit patient for IV Abx (broad-spectrum penicillin with b-lactamase inhibitor/ a cephalosporin/a quinolone/gentamicin)
Which Abx are used in pyelonephritis?
Broad-spectrum penicillin with b-lactamase inhibitor/ a cephalosporin/a quinolone/gentamicin
Abx of choice in pregnant women with pyelonephritis?
IV cefalexin
Abx of choice in pregnant women with UTI?
Oral nitrofurantoin or cefalexin
Define urolithiasis
Renal tract calculi/renal stones/urolithiasis are hard masses that form in the urinary tract
Pathophysiology of renal stone formation?
Formed due to over-saturation of the urine
How can renal stone formation lead to blockage?
Stones can grow large in size, fill the hollow structures of the kidney or even travel down the ureter
Lodging of the stone in the ureter blocks the flow of urine and may result in pain.
What is the most common type of renal stone?
Calcium based stones (80%)
What are the 4 main types of renal stones?
- Calcium based (80%)
- Struvite (5-10%)
- Uric acid (5-10%
- Cysteine (1%)
What are struvite stones made up of?
Magnesium, ammonium & phosphate
There are two types of calcium based renal stones. What are they? Which is the most common?
Calcium oxalate (most common)
Calcium phosphate (less common)
Which type of renal stone often leads to large, staghorn calculi?
Struvite
Are renal stones more common in men or women?
Men
Are renal stones more common in older or younger generation?
Younger (<65 y/o)
What & of western population do renal stones affect?
2-3% (very common)
What are the major predisposing factors of calcium based renal stones?
- Hypercalcaemia
- Low urine output
- High doses of vitamin D
- High purine/low Na/low K diet
What factors can cause hypercalcaemia that can lead to calcium based renal stones?
- Calcium supplementation
- Hyperparathyroidism
- Cancer (e.g. myeloma, breast or lung cancer)
What is the major predisposing factor to struvite renal stones?
Recurrent upper UTIs
Why do recurrent upper UTIs predispose to struvite stone formation?
Bacteria (UTIs) can hydrolyse the urea in urine to ammonia which can make urine more alkaline, leading to struvite stones
What is the most common organism that causes UTIs that lead to struvite renal stones?
Proteus infection → causes alkalinisation of the urine which leads to staghorn calculi
Uric acid stones often have no predisposing factors. However, which condition can increase the risk?
Gout → due to hyperuricaemia
What type of diet can predispose to uric acid stones?
Diet rich in purine (kidney, liver, anchovies, sardines and spinach), alcohol, gout, CKD → leads to hyperuricaemia
What is the major predisposing factor to cysteine renal stones?
Homocystinuria – an autosomal recessive inherited metabolic disorder which predisposes to recurrent renal stones and UTIs
Give some risk factors for renal stones
- Low fluid intake
- Urinary tract malformations e.g. horseshoe kidney
- UTIs
- Cystinuria (congenital)
- High sodium intake
- 1ary hyperthyroidism
- Hypervitaminosis D
- Sarcoidosis
- Cushing’s syndrome
- Milk-alkali syndrome
What are the 2 major complications of renal stones?
- Obstruction → leading to AKI
- Infection → with obstructive pyelonephritis
Differentials to rule out in potential renal stones (i.e. abdo pain)?
- AAA – rule out in men >65 with flank pain (triad: syncope, hypotension & back pain)
- Ectopic pregnancy (any woman presenting with abdominal pain)
- Pyelonephritis
- MSK pain
- Shingles
- Colitis
- Bowel cancer
- Renal cancer
- Hydronephrosis
- Gallstones
What is the main presenting complaint in symptomatic renal stones?
Renal colic
Describe renal colic
- Unilateral loin to groin pain that can be excruciating (‘worse than childbirth) → patient can’t stop moving
- Colicky (fluctuating in severity) as the stone moves and settles
- Caused by increased peristalsis around the site of obstruction
Give some other signs & symptoms of renal stones
- Haematuria (90% microscopic)
- N&V
- Reduced urine output
- Symptoms of sepsis if infection present e.g. fever, sweats
- Presentation of hypercalcaemia
Does haematuria in renal stones tend to be micro or macroscopic?
90% microscopic
What is the classic presentation of hypercalaemia?
‘Moans, bones, stones and groans’
This refers to depressed mood, MSK pain, renal stones and abdominal pain
What is the 1st line imaging in renal stones?
Non-contrast CT of kidneys, ureter and bladder (CT KUB)
Who should not be offered at CT KUB in renal stones? What can be offered instead?
Women <40 y/o shouldn’t really get this 1st line due to radiation risk → offer US KUB instead
What bedside investigations can be performed in renal stones?
- Pregnancy test
- Urine dipstick → haematuria, possible infection
- Vital signs
- Glucose
- ECG
- Beside USS (FAST)
What bloods can be taken in renal stones?
- FBC – WCCs & neutrophils likely to be raised
- U&Es – creatinine & urea likely to be raised
- LFTs
- CRP
- Serum calcium
AXR can also be used to look at renal stones. Describe the presentation of
a) calcium based stones
b) uric acid stones
c) struvite stones
d) cysteine stones
a) smooth, opaque, silky
b) not visible (radiolucent)
c) staghorn calculus
d) yellow, semi-opaque
Which type of renal stone is not visible on AXR?
Uric acid (radiolucent)
Which type of renal stone appears yellow on AXR?
Cysteine
What is a staghorn calculus?
This is where the stone forms in the shape of the renal pelvis, giving it a similar appearance to the antlers of a deer stag (the body sits in the renal pelvis with horns extending into the renal calyces).
What is the management in renal stones <5mm with no signs of obstruction?
Watchful waiting → 50-80% chance will pass spontaneously
What lifestyle measures should be advised in renal stones?
- Increase oral fluid intake (2-3 litres per day)
- Reduce dietary salt intake
- Maintain normal calcium intake (low dietary calcium might increase risk of stones)
Which drug is used in medical expulsive therapy in renal stones?
tamsulosin
What is 1st line analgesic in renal stones?
PR diclofenac
Most common surgical intervention in renal stones?
Extracorporeal shock wave lithotripsy (ESWL) → required in stones >10mm or where there is complete obstruction/infection
Which drug can be offered for hypercalciuria in renal stones?
Thiazides
Which drug can be offered for uric acid stones?
Allopurinol or potassium citrate
Define hydronephrosis
Swelling of one or both kidneys as a result of the build-up of urine. Can also be found in unborn babies during US scans (antenatal hydronephrosis).
Give some risk factors for hydronephrosis
- Pregnancy
- Kidney stones
- Enlarged prostate (BPH)
- Narrowing of ureters e.g. injury, infection, surgery
- Neurogenic bladder
- Cancer
- Pelvic organ prolapse
- Vesicoureteral reflex
Why can pregnancy predispose to hydronephrosis?
possibly due to the increased amount of urine the baby produces in the later stages of pregnancy
Why can vesicoureteral reflux lead to hydronephrosis?
the valve that controls the flow of urine between the bladder and ureters does not function properly, allowing urine to flow back up to the kidneys
Complications of hydronephrosis?
- Can increase risk of UTIs
- In severe cases, can lead to scarring of kidneys and kidney failure
Prognosis of antenatal hydronephrosis?
Often resolves on its own and will cause no long-term problems for mother or baby
Symptoms of hydronephrosis?
- Renal/ureteric colic: describes an acute and severe loin pain when a urinary stones obstructs the flow of urine
-
Pain in back or sides:
- Can be sudden and severe or a dull ache
- May be worse after drinking lots of fluids
- Symptoms of a UTI: frequency, dysuria, pain on urinating, fatigue, fever
- Blood in urine
- Urinating less often than you used to or with a weak stream
What is the diagnostic imaging investigation for hydronephrosis?
US
1st line management of hydronephrosis?
drain urine out of kidneys by inserting catheter
THEN treat underlying causes e.g. remove kidney stones
Define AKI
Defined as a rapid (within 7 days) and sustained (>24 hours) deterioration in kidney function resulting in oliguria and a rise in serum urea and creatinine.
Define oliguria
<0.5ml/kg/hour
Is AKI reversible?
yes
What classification system is used in AKI?
KDIGO
What is the diagnostic criteria for an AKI? (urine output, serum creatinine)
- Urine output <0.5ml/kg/hour for 6 hours
- Serum creatinine increase 1.5x baseline over 7 days
- Serum creatinine increase by 0.3mg/dL in 48 hours