Overview
Definition:
Suprapubic aspiration (SPA) is a method of obtaining a sterile urine sample directly from the urinary bladder by transabdominal puncture above the pubic bone
It is considered the gold standard for obtaining uncontaminated urine cultures in infants and young children when other methods are unsuccessful or unreliable.
Epidemiology:
Urinary tract infections (UTIs) are common in infants and young children, with estimates varying by age and sex
SPA is indicated in situations where obtaining a reliable urine sample is critical for diagnosis and management, particularly in neonates and infants younger than 3 months presenting with symptoms suggestive of UTI.
Clinical Significance:
Accurate and timely diagnosis of UTI is crucial in pediatric patients to prevent complications such as renal scarring, hypertension, and chronic kidney disease
SPA provides a sterile urine sample, minimizing contamination that can lead to false-positive or false-negative results with less invasive methods like bag collection
This is vital for appropriate antibiotic selection and management.
Indications
Absolute Indications:
Suspicion of UTI in infants and neonates presenting with fever of unknown origin, lethargy, poor feeding, vomiting, or other non-specific symptoms
When other methods (e.g., clean catch, catheterization) are unsuccessful or yield contaminated results
Diagnosis of UTI in neurologically impaired children or those with voiding dysfunction where voluntary sample collection is difficult.
Relative Indications:
Suspected UTI in older children with difficulty in voiding or when rapid confirmation is needed
Obtaining urine for specific biochemical or microbiological analysis requiring a sterile sample.
Contraindications:
Presence of abdominal distension making bladder palpation difficult
Known bladder anomalies or previous abdominal surgery in the suprapubic region
Coagulopathy or bleeding disorders
Very young neonates with significant abdominal wall edema
Absence of a palpable or sonographically visualized bladder.
Ultrasound Guidance
Rationale For Ultrasound:
Ultrasound guidance significantly improves the success rate and reduces complications of SPA
It allows for precise visualization of the bladder, determination of its distension, and identification of the optimal needle entry point, avoiding adjacent structures like bowel loops or major blood vessels.
Equipment Needed:
A sterile ultrasound transducer (preferably curvilinear or phased array for better penetration in older children, or linear for neonates), sterile coupling gel, sterile drapes, sterile gloves, antiseptic solution (e.g., chlorhexidine), local anesthetic (e.g., 1% lidocaine without epinephrine) for older children, sterile aspiration needle (e.g., 23-25 gauge), sterile syringe (5-10 mL), and sterile collection tubes.
Procedure With Ultrasound:
Position the patient supine
Apply antiseptic solution to the suprapubic region
Perform ultrasound to identify the distended bladder, measure its depth from the skin, and assess for any intervening structures
Mark the optimal puncture site, typically in the midline, approximately 1-2 cm superior to the pubic symphysis
In older children, infiltrate local anesthetic
Introduce the needle at a 30-45 degree angle to the skin, directed towards the bladder dome, under continuous ultrasound visualization
Aspirate urine gently
If the bladder is not adequately distended, consider administering a small amount of sterile water or saline intrathecally or administering a diuretic such as furosemide (if appropriate and safe) and re-evaluating after 30-60 minutes
Once urine is obtained, withdraw the needle smoothly
Apply gentle pressure to the puncture site
Send the urine for laboratory analysis immediately.
Diagnostic Approach
History Taking:
Focus on fever of unknown origin, feeding intolerance, vomiting, irritability, or altered urine output
Inquire about previous UTIs or known urinary tract abnormalities
Note any risk factors for UTI.
Physical Examination:
Assess vital signs, particularly temperature
Perform a thorough abdominal examination to assess for distension, tenderness, or masses
Palpate the suprapubic area for bladder distension
Evaluate for signs of sepsis or dehydration.
Investigations:
Urine analysis (dipstick and microscopy): looking for leukocytes, nitrites, and bacteria
Urine culture and sensitivity: essential for definitive diagnosis and antibiotic selection
Ultrasound of the urinary tract: to assess for hydronephrosis, bladder abnormalities, or other structural anomalies
Blood tests: CBC, electrolytes, renal function tests, C-reactive protein (CRP) if sepsis is suspected.
Interpretation Of Results:
A positive urine culture with >10^5 colony-forming units (CFU)/mL from a suprapubic aspirate is diagnostic of UTI
Lower colony counts (e.g., >10^4 CFU/mL) may be considered significant in symptomatic infants
Pyuria (presence of white blood cells in urine) on microscopy further supports the diagnosis.
Management
Initial Management:
Once UTI is confirmed, initiate prompt antibiotic therapy based on local resistance patterns and suspected organism, pending culture results
Ensure adequate hydration and monitor vital signs closely.
Medical Management:
Antibiotic selection depends on the presumed pathogen, local resistance patterns, and patient age
Common empiric choices for infants include ampicillin with gentamicin, or third-generation cephalosporins
Once culture results are available, antibiotics should be tailored to the identified organism and its sensitivity profile
Duration of treatment is typically 7-14 days.
Supportive Care:
Provide antipyretics (e.g., paracetamol, ibuprofen in appropriate doses) for fever
Maintain adequate fluid intake to prevent dehydration
Monitor urine output and signs of clinical improvement
Close monitoring for signs of sepsis or complications is essential.
Complications
Early Complications:
Bleeding at the puncture site, hematuria, bladder perforation (rare with ultrasound guidance), abdominal wall cellulitis or abscess, transient lower abdominal pain, intestinal perforation (very rare).
Late Complications:
Urinary tract fistulae (extremely rare), potential for missed diagnoses if not performed correctly
Adhesions at the puncture site (very uncommon).
Prevention Strategies:
Strict adherence to aseptic technique
Use of ultrasound guidance to visualize the bladder and avoid adjacent structures
Proper needle angle and depth
Adequate bladder distension
Gentle aspiration technique
Careful post-procedure monitoring.
Key Points
Exam Focus:
SPA is the gold standard for sterile urine culture in infants
Ultrasound guidance is essential for safety and efficacy
Key indications include suspected UTI in neonates and infants <3 months with non-specific symptoms
Contraindications include abdominal distension and lack of bladder visualization
Complications are rare with proper technique.
Clinical Pearls:
Ensure adequate bladder distension before aspiration
if not, consider rehydration or diuretic administration
For infants, a curvilinear transducer is often preferred for better penetration
A 30-45 degree angle of needle insertion is typical
Send urine for culture immediately after collection
Recognize that even with sterile techniques, trace contamination can occur, but SPA significantly minimizes this risk.
Common Mistakes:
Performing SPA without adequate bladder distension
Using the wrong needle angle or depth, increasing risk of bowel injury
Failure to use ultrasound guidance
Contaminated sample collection despite SPA due to poor technique
Delaying urine sample analysis
Not considering absolute contraindications.