Episode 69 – Urinary Tract Infections

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We cover Free Open Access Medical Education (FOAM) from a recent Emergency Medicine Cases podcast and First10inEM blog post by Dr. Justin Morganstern regarding urinary tract infections (UTIs).   This podcast and blog tackle common issues in UTI diagnosis and treatment, including the following points:

  • UTI is a clinical diagnosis, a dirty urine does not mean the patient has a UTI
  • Urinalyses are more complicated to interpret than we probably understand

The Core Content

Rosen’s Emergency Medicine (8th ed), Chapter 99; Tintialli’s Emergency Medicine (8th ed), Chapter 91; IDSA Guidelines for Treatment and Asymptomatic Bacteriuria

UTI diagnosis

Asymptomatic bacteriuria

UTI Treatment

Rosh Review Emergency Board Review Questions

A 6-year-old girl presents with 4 days of lower abdominal pain. The patient complains of dysuria. On exam, the patient is afebrile and has mild tenderness to palpation in the suprapubic area. No costovertebral tenderness is elicited on exam. A clean-catch urine sample is sent for urinalysis. If positive, which of the following is the most specific to confirm the diagnosis?

A. Glucose

B. Leukocyte esterase

C. Nitrites

D. WBCs (>5 per high power field)

Answer

C. The patient’s presentation is consistent with an uncomplicated urinary tract infection (UTI). The most common cause of a UTI in children >1 year of age is E. coli. Nitrites normally are not found in urine but result when bacteria reduce urinary nitrates to nitrites. Many Gram-negative and some Gram-positive organisms are capable of this conversion, and a positive dipstick nitrite test indicates that these organisms are present in significant numbers (i.e., more than 10,000 per mL). This test is specific (92%–100%) but not highly sensitive (19%–48%). A positive result is helpful, but a negative result does not rule out UTI. The nitrite dipstick reagent is sensitive to air exposure, so containers should be closed immediately after removing a strip. After 1 week of exposure, 33% of strips give false-positive results, and after 2 weeks, 75% give false-positive results. Non-nitrate-reducing organisms also may cause false-negative results, and patients who consume a low-nitrate diet may have false-negative results.

Glucose (A) normally is filtered by the glomerulus, but it is almost completely reabsorbed in the proximal tubule. Glycosuria occurs when the filtered load of glucose exceeds the ability of the tubule to reabsorb it (i.e., 180–200 mg per dL). Etiologies include diabetes mellitus, Cushing’s syndrome, liver and pancreatic disease, and Fanconi’s syndrome. Leukocyte esterase (B) is produced by neutrophils and may signal pyuria associated with UTI. It has a sensitivity of 72%­–97% and specificity of 41%–86%. Leukocyte casts in the urinary sediment can help localize the area of inflammation to the kidney. Organisms such as Chlamydia and Ureaplasma urealyticum should be considered in patients with pyuria and negative cultures. Other causes of sterile pyuria include balanitis, urethritis, tuberculosis, bladder tumors, viral infections, nephrolithiasis, foreign bodies, exercise, glomerulonephritis, and corticosteroid and cyclophosphamide use. Leukocytes (D) may be seen under low- and high-power magnification. Men normally have fewer than 2 white blood cells (WBCs) per HPF; women normally have fewer than 5 WBCs per HPF; >5 WBCs/HPF is associated with a 90%–96% sensitivity and 47%–50% specificity.

A 24-year old woman presents with URI symptoms. She is 32 weeks pregnant. As part of her work-up, you order a urinalysis, which shows 2+ bacteria with no WBCs. Two days later, the lab calls you and informs you that the urine culture is positive. You call the patient back and she denies symptoms of urinary tract infection. With regards to the urine culture results, what treatment is indicated?

A. Cephalexin 500 mg QID for 7 days

B. Ciprofloxacin 500 mg QID for 7 days

C. No treatment is necessary

D. Trimethoprim-sulfamethoxazole 1 DS tablet BID for 3 days

Answer

A. The patient has asymptomatic bacteriuria of pregnancy confirmed by a positive urine culture and should be treated with an oral antibiotic that is known to be safe in pregnancy, such as cephalexin 500 mg QID for 7 days. Asymptomatic bacteriuria is common in the general population and in most scenarios does not require therapy. However due to the high risk of complication seen during pregnancy, it should be treated with antibiotics. It is seen in 2-10% of pregnant women and is commonly due to E. coli. Pregnant women have an increased risk of developing urinary tract infections due to the pressure that the enlarged uterus exerts on the ureters and bladder, incomplete emptying during voiding and impaired ureteral peristalsis from progesterone-induced relaxation of the ureteral smooth muscle. Complications of untreated asymptomatic bacteriuria include development of a lower urinary tract infection, pyelonephritis, renal abscess, renal failure, bacteremia, sepsis, intrauterine growth retardation, premature labor and neonatal death. Treatment options generally include cephalosporins, such as cephalexin, amoxicillin (or amoxicillin-clavulanate) and nitrofurantoin. All of which are recognized as Category B by the Food and Drug Administration; meaning that animal studies have failed to show a risk to the fetus. Treatment duration should be for 7-10 days.

Ciprofloxacin (B) and trimethoprim-sulfamethoxazole (D) are Category C and D, respectively, and therefore should be avoided in pregnancy when possible. Because there is increased risk for complication during pregnancy, antibiotic treatment (C) is recommended.

References:

Gupta K et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases.  Infect Dis (2011) 52 (5): e103-e120.

Nicolle L et al. Infectious Diseases Society of America Guidelines for the Diagnosis and Treatment of Asymptomatic Bacteriuria in Adults.   Infect Dis (2005) 40 (5): 643-654.

Rosen’s Emergency Medicine, 8th ed. Chapter 99.

Tintinalli’s Emergency Medicine, 8th ed.  Chapter 91.

Episode 21 – Acute Kidney Injury

(ITUNES OR LISTEN HERE)

The Free Open Access Medical Education (FOAM)

Dr. Josh Farkas of the PulmCrit blog has produced a couple of blog posts on the importance of renal protection in sepsis, Renoresuscitation: Sepsis resuscitation designed to avoid long-term complications and Renal microvascular hemodynamics in sepsis: a new paradigm.  Much of this is theoretical and certainly not something that is standard practice, rathery a theory extrapolated from subgroups of several trials.

Suggested renoresuscitation measures:

(1) Avoid renal failure – avoid nephrotoxins (many antibiotics, NSAIDs, ace-inhibitors), avoid hyperchloremic metabolic acidosis.

(2) Avoid volume overload – treating decreased urine output by flooding a patient with fluids is not necessarily the best move.

(3) Protect the glycocalyx of the endothelium – this suggestion proffers more questions than answers. Steroids? Albumin? Certain vasopressors?  Stay tuned, as we’re not really certain what this entails.

The Bread and Butter

We summarize some key topics from Rosenalli, that’s Tintinalli (7e) Chapter 91; Rosen’s (8e) Chapter 97.  But, don’t just take our word for it.  Go enrich your fundamental understanding yourself.

Acute Kidney Injury – typically a creatinine 1.5-2x the patient’s baseline is classified as acute kidney injury.  Urine output can be increased initially but determine whether a patient is making urine and how much, as urine output <0.5 mL/kg/h qualifies as AKI.

RIFLE criteria
RIFLE criteria

Importance – AKI is associated with worse outcomes, although it’s unclear as to whether this is merely a marker of

  • Found in 35-65% of admissions to the intensive care unit, in 5-20% of hospital admissions.  Furthermore, AKI is associated with higher mortality.
  • Renal failure can also cause significant problems for the patient such as electrolyte abnormalities (hyperkalemia the most worriesome, but also hyperphosphatemia) and pulmonary edema.

Etiology – many causes of AKI are reversible or amenable to treatment.

Prerenal – this is one of the most common causes of acute kidney injury and basically is caused by decreased blood flow to the kidney.  Associated with a high BUN/creatinine ratio, increased urine osmolality, a urine sodium concentration less than 20 mEq/L, and FENa less than 1% (this is why getting urine sodium and a concurrent chemistry panel is key).

  • Hypovolemia – volume depleted, hemorrhage, intravascular volume depletion from congestive heart failure or cirrhosis.
  • Hypotension – poor cardiac output (heart failure, valvular problems), shock
  • Decreased flow through the renal artery disease – Nonsteroidal anti-inflammatories: inhibit prostaglandins in the afferent arteriole.  ACE inhibitors prevent the conversion of angiotensin I to angiotensin II, leading to decreased levels of angiotensin II, which when absent decreases the GFR because of dilatation of the efferent arteriole.

Post Renal (Obstructive) – Check out Episode 2 on urologic emergencies.

  • Benign prostatic hypertrophy (BPH) is the most common cause but medications such as anticholinergics and pseudoephedrine. Trauma, stones, strictures, and malignancy can also cause obstruction.

Intrinsic acute renal failure divided into: tubular disease (most common), glomerular disease, vascular disease and interstitial disease.

  • Least common form of AKI in the ED, more common in inpatients.
  • Acute Tubular Necrosis (ATN) most common cause – via nephrotoxins such as aminoglycosides and contrast.
  • Granular “muddy brown” casts – think of necrosis from the “N” in ATN and necrosis tends to be dark.

Indications for emergent dialysis – AEIOU

A- Acidosis

E- Electrolyte emergencies (hyperkalemia!)

I-  Intoxication with dialyzable toxins (ethylene glycol)

O- Overloaded with volume

U- Uremia

 Generously Donated Rosh Review Questions 

Question 1. A 72-year-old man is brought to the ED from a nursing home for evaluation of oliguria. He is found to have an acutely elevated BUN and plasma creatinine from baseline. A Foley catheter is placed; his urine sodium (UNa) is measured below 20 mEq/L and fractional excretion of sodium (FENa) below 1%. [polldaddy poll=8545511]

Question 2.  A 54-year-old man presents to the ED in acute renal failure (ARF). [polldaddy poll=8545512]

Answer 1.  D. This patient’s oliguria with acutely elevated BUN and plasma creatinine suggest that he is in acute renal failure (ARF). His UNa <20 mEq/L and FENa <1% indicate that he has intact reabsorptive function and is able to conserve sodium. This is consistent with prerenal azotemia as the cause for his ARF.

Acute tubular necrosis (ATN) (A), loop diuretics (e.g., furosemide) (B), and osmotic diuresis (e.g., mannitol) (C)all lead to UNa >20 mEq/L and FENa >1% because there is impairment in the ability to concentrate the urine. In such cases, a high-sodium load is excreted.

Answer 2. A.   Acute tubular necrosis (ATN) is a severe form of impairment of tubular epithelial cells caused by ischemia or toxic injury. It is a leading cause of ARF. One of its hallmarks is the presence of brown granular casts on urinalysis. These contain cellular debris rich in cytochrome pigments. In contrast, hyaline casts (B) are usually nonspecific but present after exercise; red cell casts (C) are indicative of glomerular hematuria (e.g., glomerulonephritis); and white cell casts (D) imply renal parenchymal inflammation (e.g., acute interstitial nephritis, pyelonephritis).

Episode 2: Urologic Emergencies

Episode 2 – Urologic Emergencies (iTunes

The Free Open Access Medical Education (FOAM) – The Skeptics Guide to Emergency Medicine (SGEM) Episode 71

The podcast reviews: Tamsulosin for ureteral stones: a systematic review and meta-analysis of a randomized controlled trial.

  • Paper’s Conclusion:  ‘Tamsulosin is a safe and effective medical expulsive therapy choice for ureteral stones. It should be recommended for most patients with distal ureteral stones before stones are 10 mm in size. In the future, high-quality multicenter, randomized and placebo- controlled trials are needed to evaluate the outcome.”

The SGEM’s analysis:  Tamsulosin is useless in most ED patients with ureteral colic unless their stone size exceeds at least 4mm.

The Bread and Butter

We summarize some key topics from the following readings,  Tintinalli (7e) Chapters 95, 97; Rosen’s (8e) Chapter 99, but the point isn’t to just take our word for it.  Go enrich your fundamental understanding yourself!

Renal Colic

Diagnostics

  • Urinalysis demonstrating microscopic hematuria.  Note: 10-15% of patients with renal colic have no hematuria
  • Imaging isn’t needed in patient’s with a history of renal colic and symptoms consistent with their previous episodes and without signs of symptoms of significant obstruction or infection.  Non-contrast CT scan is currently the standard diagnostic imaging of choice and bedside ultrasound may be used to look for hydronephrosis, but isn’t great for picking up stones.  The Ultrasound Podcast guys have a great episode on the topic.  Plain films (KUBs) are only useful in following the location of the stone after CT scan.
  • Make sure you’re not dealing with a tricky abdominal aortic aneurysm.

Management

  • Analgesics – nonsteroidals and, if needed, narcotics
  • Anti-emetics
  • Use of alpha-antagonist such as tamsulosin is controversial, as indicated in The SGEM podcast.  Tintinalli supports the use of these agents, whereas Rosen’s cautions that use of this medication is controversial.
  • Disposition – home with a strainer to catch the stone and outpatient urology follow up if patient has adequate pain control and oral intake and lacks significant infection or obstruction.  Remember, stones <5mm are going to pass on their own most of the time (~95%), whereas patients with stones >8mm will undergo intervention 95% of the time.

Infected Kidney Stones – Suspect in patients with SIRS criteria or those that appear sick (don’t forget that temperature <36 C, 10% bands, <4K white blood cells, and elevated respiratory rate are all part of SIRS) and in those with signs of infection on their urinalysis.

Management

  • Urgent or emergent urologic consultation to evaluate the need for drainage and for relief of the obstruction.
  • Treat sepsis and shock with good sepsis care including antibiotics and fluid resuscitation but these patients may need immediate operative intervention by urology for adequate source control.  This may include a stent or percutaneous nephrostomy tube.  Call urology.

Acute Urinary Retention

Causes

  • Spontaneous – Benign Prostatic Hypertrophy (BPH)
  • Precipitated – a host of medications (pseudoephedrine, NSAIDs, anticholinergics), anesthesia, strictures, masses, spinal cord compression (most sensitive finding in cauda equina!), infection

Diagnosis

  • Palpate the patient’s abdomen, feel for a distended bladder
  • Ultrasound, checking for a post-void residual >150 cc (LxWxH x 0.52 – although, notably there are a variety of coefficients to multiply by based on the shape)
  • Check a urinalysis, BUN, creatinine
  • History and physical should guide further testing with regard to etiology

Management

  • Treat the underlying cause (stop the offending medication, treat the infection, etc)
  • Place a foley catheter to relieve the obstruction.  There is some literature on spontaneous voiding trials in the ED but this isn’t standard (see this Academic Life in Emergency Medicine article).
  • Urology follow up within 3-7 days
  • Admit patients with signs of sepsis, co-morbidities, or renal insufficiency (or those that won’t follow up otherwise).

Generously donated Rosh Review questions (scroll for answers)

Question 1 [polldaddy poll=8057572]

Question 2 [polldaddy poll=8077276]

Listen 

 

Answers:

1) C.  The 3 primary predictors of stone passage without the need for surgical intervention are stone size, stone location, and the degree of patient pain at discharge. The most important factor, however, is calculus size. Approximately 90% of calculi smaller than 5 mm pass spontaneously within 4 weeks.

2) A.  Indications for hospitalization: intractable nausea/vomiting, severe dehydration, pain, associated UTI, solitary or transplanted kidney, high grade obstruction.

References:

Tintinalli (8e) Chapter 97.  Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. 2011.

Ban KM, Easter JS.  Selected Urologic Problems.  Chapter 99.  Rosen’s Emergency Medicine.  (8e) p 1326-1354

Yen D, Lee C. Chapter 95. Acute Urinary Retention. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. 2011.