Suprapubic Aspiration

Anatomy and Physiology

SPA involves inserting a needle through the lower abdominal wall into the bladder to obtain a urine specimen. Understanding the relevant anatomy and physiology is crucial for performing this procedure safely and effectively. The bladder is a hollow, muscular organ in the pelvis posterior to the pubic symphysis. The bladder wall comprises 3 layers: the innermost mucosal layer, the muscular detrusor layer, and the outermost serosal layer. The bladder is covered by the peritoneum superiorly, but in the suprapubic region, the peritoneum is lifted away as the bladder fills, reducing the risk of bowel injury during SPA.

The primary physiological consideration in SPA is bladder filling. The bladder should be sufficiently distended with urine to ensure that it is easily accessible and to reduce the risk of injury to surrounding structures. When the bladder is full, it rises into the abdomen, pushing the peritoneum away from the needle's path. This separation creates a safe window for needle insertion without risking peritoneal or bowel injury.

The procedure involves inserting a needle directly into the bladder through the skin, subcutaneous tissue, and abdominal muscles. Once the needle is in the bladder, urine is aspirated, providing a sterile sample for analysis. Because the bladder is a sterile environment, SPA avoids contamination, making it the most reliable method for collecting urine for culture and analysis.

In infants and young children, the bladder lies higher in the abdomen, superior and posterior to the pubic symphysis. The key anatomical landmarks for SPA in this age group are the suprapubic crease and the umbilicus. To locate the needle insertion site, clinicians envision an imaginary line from the umbilicus to the suprapubic crease, inserting the needle at the midpoint of this line.[7] The needle passes through the skin, soft tissues, rectus sheath, peritoneum, and bladder wall.

The bladder is positioned lower in the pelvis in adults, sitting retropubically. The primary anatomical landmark for SPA in adults is the pubic symphysis. Clinicians must be cautious of the peritoneal attachments of the bladder dome, as cannulating this area can risk injury, such as perforation of the intraperitoneal bladder or intestine. Awareness of major vascular structures, like the common and internal iliac arteries lateral to the bladder, is also important. The suprapubic region, located just above the pubic symphysis, is relatively free of large blood vessels and nerves, reducing the risk of injury during the procedure. The ideal needle insertion site is in the midline, about 1 to 2 cm above the pubic symphysis, where the bladder is closest to the skin.

Indications

The indications for SPA are:

• Febrile child aged 2 to 24 months with unknown source of fever [2]
• Need for sterile urine collection when urethral catheterization is not possible, such as in cases of: 
  • Labial adhesions
  • Labial edema
  • Phimosis 
  • Children with a history of intraurethral or vaginal surgery [8][9]
• Aid in the diagnosis of retrograde ejaculation: To distinguish true retrograde ejaculation from retained urethral ejaculate [10]
• Bladder outlet obstruction (urinary retention) secondary to urethral stricture, urethral injury, malignancy, acute prostatitis, or prostatic hyperplasia: Mainly when urethral catheterization is not possible
• As part of a suprapubic tube placement procedure: Suprapubic aspiration is performed immediately before guidewire placement
• Spinal cord injury in which the patient is unable to void voluntarily
• Suprapubic needle placement: Can also be used to puncture a nondeflating Foley catheter balloon with ultrasound guidance [11]

Contraindications

Contraindications to SPA include:

• Abdominal distension [7]
• Abdominal wall skin trauma or scarring
• Coagulopathy
  • Bleeding disorders such as thrombocytopenia or hemophilia
  • Elevated international normalized ratio 
• Evidence of intervening bowel or intestines
• Major abnormalities of the genitourinary tract
• Nonpalpable bladder or the patient has urinated within 1 hour before the procedure
• Patients with bladder cancer
• Organomegaly or other intraabdominal organ abnormalities [7]
• Overlying soft tissue infections of the abdominal wall
• Uncooperative patient
• Severe ascites or morbid obesity.

Equipment

The following equipment is typically required to perform a SPA:

• Antiseptic solution (povidone-iodine, chlorhexidine, alcohol)
• Sterile gloves
• Sterile drape or towel 
• Topical anesthetic cream (optional) [9]
• 1% lidocaine
• 5-mL syringe for anesthetic solution
• 10-mL syringe for aspiration sample
• In young children: 1.5- to 3-inch (or longer) 22-gauge or spinal needle for aspiration
• In older children and adults: 3-inch (or longer) 22-gauge or spinal needle for aspiration
• If the practitioner intends to leave a guide wire for suprapubic tube placement, an 18-gauge or larger needle is required to allow a 0.035" guidewire passage.
• 25 gauge needle for drawing anesthetic solution
• A sterile urine collection container
• Sterile gauze
• Bandage
• If performing the procedure with ultrasound guidance, the following will also be required:
  • Portable ultrasound machine
  • Sterile ultrasound gel
  • Sterile ultrasound transducer cover

Personnel

SPA is a simple and safe procedure usually performed by an emergency clinician, pediatrician, or urologist. This procedure is not generally considered within the scope of practice of the nursing staff.[1] Since suprapubic aspiration most commonly involves patients younger than 2 years, having an assistant involved during the procedure is recommended to increase the success rate.[7] 

Preparation

The following steps should be taken to prepare for an SPA:

Preoperative

• Obtain informed consent from the patient or family/guardian in pediatric cases.[9]

Intraoperative

• Apply the antiseptic solution over the lower abdomen from the umbilicus to the pubic bone.
• Apply sterile drapes over the lower abdomen.
• Consider sedation as appropriate.

Technique or Treatment

Positioning

Infants and young children are positioned supine, with an assistant standing at the head of the bed, holding the patient in a frog-leg position. Adults are also placed in a supine position. 

Bladder Distention Confirmation

Ensure the bladder is full to increase the likelihood of successful urine aspiration. Decreased bladder volume secondary to dehydration has been found to decrease the success of the procedure.[12] This is an important concept, especially given that some patients who are candidates for suprapubic aspiration will be febrile and volume-depleted. Bladder distention is confirmed through palpation, percussion, or using ultrasound guidance. Ultrasound to visualize the bladder greatly increases the safety profile and likelihood of a successful procedure.[13][14][15] On ultrasonography, the bladder appears anechoic with posterior enhancement.[16] In children, the bladder is best visualized with the linear array transducer, whereas in adults, it is best visualized with the curvilinear transducer. If formal ultrasonography is unavailable, a bladder scan can still be helpful in identifying the location of maximal bladder distension.[17] 

Identification of Insertion Site

Locate the midline pubic symphysis. The needle injection site is 1 to 2 cm above this spot in children and about 2 to 4 cm above this spot in adults.[9]

Skin Preparation

To reduce the risk of infection, the skin over the intended insertion site is thoroughly cleaned with an antiseptic solution such as chlorhexidine or povidone-iodine.

Anesthesia

If using local anesthesia, infiltrate a small amount of 1% lidocaine into the soft tissues and abdominal wall muscles at the needle insertion site.[9] Local anesthesia is optional in children since it is considered to cause as much pain as the aspiration.[8][9]

Needle Insertion and Confirmation

In children, insert the aspiration needle 1 to 2 cm above the midline of the pubic symphysis at a slightly cephalad angle so it is 10 to 20 degrees from vertical. In adults, insert the aspiration needle 2 to 4 cm above the midline of the pubic symphysis at a slightly caudad angle.[8] Advance the needle while applying mild negative pressure until urine is aspirated. If using ultrasound guidance, visualize the needle entering the bladder.[9] 

Guidewire Insertion (Optional)

If placing a guidewire, advance the wire into the needle, allowing it to curl in the bladder, leaving only a small wire portion outside. Take care not to let the end of the wire disappear or retract inside the needle so control is maintained. Remove the needle over the guidewire.

Needle Withdrawal

After obtaining the urine sample, the needle is carefully withdrawn. Pressure is applied to the site to minimize bleeding or hematoma formation. The urine sample is then sent for analysis. A bandage or dressing is applied to the aspiration site.

Postprocedure Care

After the procedure, the patient’s abdomen should be examined and palpated to evaluate for signs of peritonitis. If the patient is discharged home, the patient should be instructed to return to the emergency department or follow up with the performing clinician for fever and erythema of the procedure site, severe abdominal pain, and child inconsolability. Some patients may require nonsteroidal antiinflammatory drugs or acetaminophen for postprocedural pain control.

Complications

Complications of suprapubic aspiration are rare, and the utilization of real-time ultrasound guidance decreases their likelihood. Minor complications include mild hematuria and bruising. Potential severe complications of this procedure include bowel wall perforation, cellulitis, gross hematuria, hemoperitoneum, and bleeding.[7][9] If bowel perforation is suspected while performing the aspiration, withdraw the needle and perform the procedure with a fresh needle. A bowel injury from this procedure is usually not clinically significant.[9] A suprapubic abscess has rarely been reported.[18] 

Clinical Significance

Key Points of Clinical Significance of SPA

The gold standard for urinary tract infection diagnosis in children

SPA is the gold standard for obtaining urine samples in infants and young children, especially those not toilet-trained. The American Academy of Pediatrics recommends SPA or catheterization for urine collection in children aged 2 to 24 months with unexplained fever, as contamination can significantly alter urine culture results.

Minimizing contamination

Traditional urine collection methods, such as bag collection or clean-catch, often result in contamination with skin flora, leading to false positives and unnecessary antibiotic treatment. SPA avoids this issue by providing a pure sample directly from the bladder, ensuring that any bacterial growth represents a true infection. A comparison of clean catch and SPA urine collection techniques on febrile children younger than 2 indicated that a significant number of patients would be misdiagnosed as negative if relying only on the clean catch urine specimen, particularly if only using a dipstick.[19] 

Urethral catheterization urine specimens in children have been shown to have a higher false negative rate than SPA samples.[20] SPA is therefore recommended in highly suspicious cases, even with a negative clean catch urine specimen.[19] Results from an observational cohort study of urine cultures of 599 children younger than 24 months, the contamination rates were 1%, 12%, and 26% in urine samples obtained by SPA, urethral catheterization, and clean catch techniques, respectively.[21] 

Utility in special populations

SPA is beneficial in patients with anatomical abnormalities, neurogenic bladder, or those with an indwelling catheter where traditional methods of urine collection may not be feasible or reliable. Additionally, it is a valuable tool for critically ill patients whose catheterization may pose a higher risk of infection.

Diagnostic accuracy

The high accuracy of SPA makes it invaluable in guiding appropriate antibiotic therapy, particularly in cases of resistant organisms or recurrent urinary tract infections. Accurate diagnosis reduces the risk of overprescription of antibiotics and helps in preventing the development of antibiotic resistance.

Use in obstructed bladder

In adults, SPA is sometimes used when there is an obstruction at the bladder outlet, making catheterization impossible. SPA can provide relief and allow for the diagnosis of the underlying condition.

Enhancing Healthcare Team Outcomes

Effective SPA performance requires a well-coordinated, interprofessional approach that emphasizes skill, strategy, and communication among healthcare professionals. Physicians, advanced clinicians, nurses, and other team members must collaborate closely to ensure patient-centered care, optimal outcomes, and safety. Clinicians must be proficient in the technique, have a solid understanding of the relevant anatomy, and be skilled in ultrasound-guided needle placement to minimize complications. Nurses play a vital role in preparing the patient, educating families about the procedure, and providing post-procedural care. Pharmacists ensure the availability and proper administration of necessary medications, such as local anesthetics, while monitoring for potential interactions.

Interprofessional communication and care coordination are critical to enhancing patient safety and team performance during SPA. A clear, shared strategy among all team members ensures that each step of the procedure is executed efficiently and safely. This includes confirming patient identification, discussing potential risks, and agreeing on complication contingency plans. Regular debriefings and continuous feedback help refine the process, reduce errors, and improve overall outcomes. By fostering a collaborative environment, healthcare teams can deliver high-quality, patient-centered care that prioritizes safety, reduces the risk of infection, and leads to better diagnostic accuracy.