Venous blood sampling is a valuable tool to help diagnose and guide surgical planning for a variety of endocrine conditions, from Cushing’s disease to functional pancreatic tumors. This is especially true in cases where the diagnosis is equivocal, or anatomic or pathological issues make discrete localization of affected tissue difficult. Generally safe and effective, this family of procedures relies on the fact that venous blood sampled close to a specific organ or tumor is more likely to show elevated levels of hormones or tumor markers than blood sampled from a more peripheral source. Thus, a positive result on venous sampling can help yield a discrete diagnosis and, often more importantly, a discrete location for the abnormal hormonal production.
Specific venous sampling procedures
Parathyroid venous sampling
Venous sampling for parathyroid hormone (PTH) is utilized to localize missed or recurrent abnormal parathyroid tissue in patients with persistent or recurrent hyperparathyroidism after attempted parathyroidectomy.
Indications:
- Utilized when sestamibi and additional imaging are inconclusive or discordant, frequently in post-surgical patients
- Performed as a preoperative outpatient examination
- Allows surgeons to perform targeted unilateral neck dissection
- Preoperative localization improves intraoperative identification of adenoma, and in turn leaves more favorable postoperative field if re-exploration is necessary (5-10% of cases)
- Reduces perioperative morbidity and operation time
Work up:
- Noninvasive imaging:
- Technetium SestaMIBI: Negative
- SPECT-CT: Negative
- Referral for venous sampling to isolate the lesion/side before surgical exploration
Procedure:
- Access via common femoral vein
- Baseline sampling of SVC or iliac (control)
- Obtain selective venous samples bilaterally, documenting catheter position for each sample
- Extensive effort to ensure good sampling of the inferior thyroid vein(s) and all veins draining into the left brachiocephalic (ieoften multiple samples)
- Often requires multiple selective catheters
- 4-5F, 80-100cm catheters with 0.035in, 145cm hydrophilic glidewire
- Though super-selective sampling is critical, sampling proximal and distal inflow may be used to assess a gradient change if unable to catheterize a small vein.
Post procedure:
- Observed for 1- 2 hrs for any discomfort or complications.
- Discharge.
Complications:
very low with the majority again being general to all venous procedures such as hematoma, thrombosis, and contrast reactions
Follow up:
To contact the referring doctor for further management
Adrenal Venous sampling
Primary aldosteronism should be suspected in patients presenting with hypertension and at least additional risk factor including: medication resistance, hypokalemia, young age (< 20 years), incidental adrenal lesion, or first degree relative with primary aldosteronism. Adrenal venous sampling (AVS) is utilized for pre-surgical localization and lateralization in cases of primary aldosteronism.
Indications:
- To Differentiate Hyper functioning adenoma vs Bilateral nodular hyperplasia
- To Locate the source of hypersecretion of
- Aldosterone
- Cortisol
- Masculinizing hormones (in conjunction with ovarian vein sampling)
Work up:
- Other tests:
- Postural challenge test,
- Measurement of plasma 18-hydroxycorticosterone,
- High resolution CT.
- AVS:
- Widely accepted as the gold standard procedure for the diagnosis of unilateral aldosteronoma.
Procedure:
- Mineralocorticoid receptor antagonists including ARBs should be stopped at least 4-6 weeks prior to AVS.
- Cosyntropin use is technically helpful as it increases adrenal blood flow, making cannulation easier, and increases overall aldosterone levels making aldosterone to cortisol levels more accurate and easier to interpret.
- Access via common femoral vein
- 5 or 6 F long sheath
- Sequential selective venous samples of right, left and infrarenal IVC obtained documenting catheter position for each sample
- Hemostasis by manual compression
Post procedure:
- Observed for 1- 2 hrs for any discomfort or complications.
- Discharge
Complications:
very low with the majority again being general to all venous procedures such as hematoma, thrombosis, and contrast reactions
Follow up:
To contact the referring doctor for further management
Sampling in Renovascular Hypertension
Renal vein renin sampling:
           Renal vein sampling can be done to evaluate renin levels in the case of renovascular hypertension. Â
Ovarian (gonadal) venous sampling:
Sampling of the venous outflow from the ovaries and adrenals can be a useful diagnostic tool in patients with suspected androgen secreting tumor.
Other venous sampling procedures
Inferior petrosal sinus sampling (IPSS):
Inferior petrosal sinus sampling (IPSS) allows sampling of venous outflow proximal to the pituitary gland, primarily done to evaluate the cause of elevated cortisol levels in cases of suspected Cushing’s disease.
Pancreatic Endocrine Venous Sampling:
           Venous sampling for pancreatic endocrine hormones can help localize small functional pancreatic endocrine tumors, especially insulinomas and, less often, gastrinomas.
Prostatic specific antigen (PSA):
When it is borderline elevated from a peripheral sample, as the PPV is low (25%) for cancer detection. Sampling of PSA from the bilateral internal iliac veins can show if the PSA truly is elevated, and raise the PPV.
The goal in mind when choosing a particular vascular access device is ‘what will provide the patient with the best way to administer the therapies required while simultaneously doing the least amount of damage to the vascular system’.
What is Venous sampling?
- Performed by an interventional radiologist using x-ray guidance (fluoroscopy).
- Minimally invasive procedure with only a puncture site; no large incisions.
- Catheter is inserted into the vein from the groin (femoral access) or Neck (Jugular access)
- Obtaining venous blood sample close to a specific organ or tumor is more likely to show elevated levels of hormones or tumor markers than blood sampled from a more peripheral source.
Types of Venous samplings?
- Parathyroid
- Adrenal
- Inferior petrosal sinus
- Renal vein
- Pancreatic
- Gonadal
- Prostatic
What does the work-up include?
- Differs based on the type of venous sampling. More information can be obtained from the center performing these procedures.
- Preprocedure blood work: CBC w PLTs, BMP, PT/INR
What does the procedure involve?
- Moderate sedation and local anesthetic
- Supine (back) position
- Length of procedure: 1~3 hours
- Discharge on the same day, with post procedure stay for 1- 2 hrs.
- Results take 1-5 days depending on the type of samplings.
What are the complications?
- very low with the majority again being general to all venous procedures such as hematoma, thrombosis, and contrast reactions
What is the recovery period?
- Follow pelvic rest for 1 month. Pelvic rest includes nothing in the vagina (e.g., no douching, no intercourse, no foreign objects, no tampons).
- Advise to take 2 weeks off from work (depending on type of job) due to moderate fatigue.
- No physical activity or heavy lifting for 48 hours after the procedure.
- Pre-UFE symptoms may persist for 3 to 6 months.
- UFE results should be seen within 1 to 2 cycles. Fibroids usually shrink enough for a change in symptoms within 3 months, ~50 % shrinkage in 6 months. Stop shrinking after 1 year.
What is the follow-up plan?
- Follow-up with referring physician, who will assist in interpretation and management.
What are the benefits?
- Helps in localization or identifying the area of abnormality and assist in management plans.
- No GENA required. Lowers sedation risks.
- Day case procedure
- Minimal risks
What are the disadvantages?
- Technical failure
- Inconclusive results
Are there any issues to consider during placement of vascular devices for access?
Image guidance
The use of ultrasound to guide access placement has greatly reduced the incidence of vascular complications. Ultrasound guided has been shown to reduce complications and improve technical success of central line placement.
Ultrasound evaluation of veins is very valuable to ensure patency before venipuncture. Ultrasound has significantly reduced the incidence of immediate complications from rates previously as high as 11.8% down to as low as 7-4%
Renal failure
In order to preserve veins for future hemodialysis access (fistula or graft), it is essential to consult with the interventional radiologist or nephrologist before placing upper extremity or subclavian lines of any type in patients who might eventually require dialysis.
Thrombosis
Thrombosis can occur within the catheter or within the vein.
Vigilance in following flushing protocols and the use of prophylactic low-dose anticoagulants where appropriate can decrease the incidence of thrombosis, which in turn reduces the infection rate as thrombus can provide a medium for bacterial growth.
Venous access device–associated venous thrombosis is treated with systemic anticoagulation, in the same way as lower extremity DVT is managed.
Infection
It is essential to differentiate between local insertion site inflammation and true infection. Infections can be divided into
- entrance-site cellulitis (which usually responds to antibiotic treatment),
- skin tract or tunnel infection, and
- catheter-related bacteremia.
Preventive use of antibiotics has not been shown to reduce the risk of infection.
Meticulous sterile technique at the time of catheter insertion, when accessing the central line, and when changing dressings is essential.
