There are few studies of the long-term outcomes of patients treated for MALS. According to Duncan, the largest and more relevant late outcomes data come from a study of 51 patients who underwent open surgical treatment for MALS, 44 of whom were available for long-term follow-up at an average of nine years following therapy. The investigators reported that among patients who underwent celiac artery decompression and revascularization, 75% remained asymptomatic at follow-up. In this study, predictors of favorable outcome included:

- Age from 40 to 60 years

- Lack of psychiatric condition or alcohol use

- Abdominal pain that was worse after meals

- Weight loss greater than 20 lb (9.1 kg)

Aortocaval compression syndrome is compression of the abdominal aorta and inferior vena cava by the gravid uterus when a pregnant woman lies on her back, i.e. in the supine position. It is a frequent cause of low maternal blood pressure (hypotension), which can be result in loss of consciousness and in extreme circumstances fetal demise.

Aortocaval compression is thought to be the cause of supine hypotensive syndrome. Supine hypotensive syndrome is characterized by pallor, tachycardia, sweating, nausea, hypotension and dizziness and occurs when a pregnant woman lies on her back and resolves when she is turned on her side.

The aorta and inferior vena cava are central vessels, the largest artery and vein. They supply blood to the heart, and the rest of the body. Thus, when there is compression due to the weight of the fetus, signs of shock (sweating, pallor, fast and weak pulse) may be experienced. Patients should be placed in a left lateral recumbent position and emergency help summoned immediately.

Treatment depends on the severity and symptoms. Treatments include:

- Endovascular stenting.

- Renal vein re-implantation.

- Gonadal vein embolization.

Decompression of the celiac artery is the general approach to treatment of MALS. The mainstay of treatment involves an open surgical approach to divide, or separate, the median arcuate ligament to relieve the compression of the celiac artery. This is combined with removal of the celiac ganglia and evaluation of blood flow through the celiac artery, for example by intraoperative duplex ultrasound. If blood flow is poor, celiac artery revascularization is usually attempted; methods of revascularization include aortoceliac bypass, patch angioplasty, and others.

A laparoscopic approach may also be used to achieve celiac artery decompression; however, should the celiac artery require revascularization, the procedure would require conversion to an open approach.

Endovascular methods such as percutaneous transluminal angioplasty (PTA) have been used in patients who have failed open and/or laparoscopic intervention. PTA alone, without decompression of the celiac artery, may not be of benefit.

Epidemiological data is elusive owing to the wide variety of clinical presentation. In the U.S., incidence is estimated to be at 5–10 cases per 100,000 per year. Minor compression of the inferior vena cava during pregnancy is a relatively common occurrence. It is seen most prevalently when women lie on their back or right side. 90% of women lying in the supine position during pregnancy experience inferior vena cava syndrome; however, not all of the women display symptoms.

Management of the underlying defect is proportional to the severity of the clinical presentation. Leg swelling and pain is best evaluated by vascular specialists (vascular surgeons, interventional cardiologists, interventional radiologists) who both diagnose and treat arterial and venous diseases to ensure that the cause of the extremity pain is evaluated. The diagnosis needs to be confirmed with some sort of imaging that may include magnetic resonance venography, venogram and usually confirmed with intravascular ultrasound because the flattened vein may not be noticed on conventional venography. In order to prevent prolonged swelling or pain from the consequences of the backed up blood from the compressed iliac vein, flow needs to be improved out of the leg. Uncomplicated cases may be managed with compression stockings.

Severe May-Thurner syndrome may require thrombolysis if there is a recent onset of thrombosis, followed by angioplasty and stenting of the iliac vein after confirming the diagnosis with a venogram or an intravascular ultrasound. A stent may be used to support the area from further compression following angioplasty. As the name implies, there classically is not a thrombotic component in these cases, but thrombosis may occur at any time.

If the patient has extensive thrombosis, it may be appropriate to consider pharmacologic and/or mechanical (also known as pharmacomechanical) thrombectomy. This is currently being studied to determine whether this will decrease the incidence of post-thrombotic syndrome.

In medicine, May-Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is a rare condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or blood clots, called deep venous thrombosis (DVT), in the iliofemoral vein.

The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots. Uncommon variations of MTS have been described, such as the right common iliac vein getting compressed by the right common iliac artery.

In the 21st century the May-Thurner syndrome definition has been expanded to a broader disease profile known as nonthrombotic iliac vein lesions (NIVL) which can involve both the right and left iliac veins as well as multiple other named venous segments. This syndrome frequently manifests as pain when the limb is dependent (hanging down the edge of a bed/chair) and/or significant swelling of the whole limb.

Evidence for the treatment of thoracic outlet syndrome as of 2014 is poor.

Inferior vena cava syndrome (IVCS) is a result of obstruction of the inferior vena cava. It can be caused by invasion or compression by a pathological process or by thrombosis in the vein itself. It can also occur during pregnancy.Pregnancy can lead to problems with blood return due to high venous pressure in the lower limbs, failure of blood return to the heart, decreased cardiac output due to obstructions in inferior vena cava, sudden rise in venous pressure which can lead to placental separation, and a decrease in renal function. All of these issues can arise from lying in the supine position during late pregnancy which can cause compression of the inferior vena cava. Symptoms of late pregnancy inferior vena cava syndrome consist of intense pain in the right hand side, muscle twitching, drop of blood pressure, and fluid retention.

Umbilical cord compression may be relieved by the mother switching to another position. In persistent severe signs of fetal distress, Cesarean section may be needed.

In a review, botox was compared to a placebo injected into the scalene muscles. No effect in terms of pain relief or improved movement was noted. However in a six-months follow-up, paresthesia (abnormal sensations such as in "pins and needles") was seen to be significantly improved.

Treatment is decompression of the quadrilateral space, with supportive therapy in recalcitrant cases.

Mortality from aortic rupture is up to 90%. 65–75% of patients die before they arrive at hospital and up to 90% die before they reach the operating room.

On cardiotocography (CTG), umbilical cord compression can present with variable decelerations in fetal heart rate.

Several methods of treatment are available, mainly consisting of careful drug therapy and surgery. Glucocorticoids (such as prednisone or methylprednisolone) decrease the inflammatory response to tumor invasion and edema surrounding the tumor. Glucocorticoids are most helpful if the tumor is steroid-responsive, such as lymphomas. In addition, diuretics (such as furosemide) are used to reduce venous return to the heart which relieves the increased pressure.

In an acute setting, endovascular stenting by an interventional radiologist may provide relief of symptoms in as little as 12–24 hours with minimal risks.

Should a patient require assistance with respiration whether it be by bag/valve/mask, BiPAP, CPAP or mechanical ventilation, extreme care should be taken. Increased airway pressure will tend to further compress an already compromised SVC and reduce venous return and in turn cardiac output and cerebral and coronary blood flow. Spontaneous respiration should be allowed during endotracheal intubation until sedation allows placement of an ET tube and reduced airway pressures should be employed when possible.

The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist. The name derives from the fact that, in the sagittal plane and/or transverse plane, the SMA and AA (with some imagination) appear to be a nutcracker crushing a nut (the renal vein).

There is a wide spectrum of clinical presentations and diagnostic criteria are not well defined, which frequently results in delayed or incorrect diagnosis.

This condition is not to be confused with superior mesenteric artery syndrome, which is the compression of the third portion of the duodenum by the SMA and the AA.

Delay in the diagnosis of SMA syndrome can result in fatal catabolysis (advanced malnutrition), dehydration, electrolyte abnormalities, hypokalemia, acute gastric rupture or intestinal perforation (from prolonged mesenteric ischemia), gastric distention, spontaneous upper gastrointestinal bleeding, hypovolemic shock, and aspiration pneumonia.

A 1-in-3 mortality rate for Superior Mesenteric Artery syndrome has been quoted by a small number of sources. However, after extensive research, original data establishing this mortality rate has not been found, indicating that the number is likely to be unreliable. While research establishing an official mortality rate may not exist, two recent studies of SMA syndrome patients, one published in 2006 looking at 22 cases and one in 2012 looking at 80 cases, show mortality rates of 0% and 6.3%, respectively. According to the doctors in one of these studies, the expected outcome for SMA syndrome treatment is generally considered to be excellent.

SMA syndrome can present in acute, acquired form (e.g. abruptly emerging within an inpatient stay following scoliosis surgery) as well as chronic form (i.e. developing throughout the course of a lifetime and advancing due to environmental triggers, life changes, or other illnesses). According to a number of recent sources, at least 70% of cases can typically be treated with medical treatment, while the rest require surgical treatment.

Medical treatment is attempted first in many cases. In some cases, emergency surgery is necessary upon presentation. A six-week trial of medical treatment is recommended in pediatric cases. The goal of medical treatment for SMA Syndrome is resolution of underlying conditions and weight gain. Medical treatment may involve nasogastric tube placement for duodenal and gastric decompression, mobilization into the prone or left lateral decubitus position, the reversal or removal of the precipitating factor with proper nutrition and replacement of fluid and electrolytes, either by surgically inserted jejunal feeding tube, nasogastric intubation, or peripherally inserted central catheter (PICC line) administering total parenteral nutrition (TPN). Pro-motility agents such as metoclopramide may also be beneficial. Symptoms may improve after restoration of weight, except when reversed peristalsis persists, or if regained fat refuses to accumulate within the mesenteric angle. Most patients seem to benefit from nutritional support with hyperalimentation irrespective of disease history.

If medical treatment fails, or is not feasible due to severe illness, surgical intervention is required. The most common operation for SMA syndrome, duodenojejunostomy, was first proposed in 1907 by Bloodgood. Performed as either an open surgery or laparoscopically, duodenojejunostomy involves the creation of an anastomosis between the duodenum and the jejunum, bypassing the compression caused by the AA and the SMA. Less common surgical treatments for SMA syndrome include Roux-en-Y duodenojejunostomy, gastrojejunostomy, anterior transposition of the third portion of the duodenum, intestinal derotation, division of the ligament of Treitz (Strong's operation), and transposition of the SMA. Both transposition of the SMA and lysis of the duodenal suspensory muscle have the advantage that they do not involve the creation of an intestinal anastomosis.

The possible persistence of symptoms after surgical bypass can be traced to the remaining prominence of reversed peristalsis in contrast to direct peristalsis, although the precipitating factor (the duodenal compression) has been bypassed or relieved. Reversed peristalsis has been shown to respond to duodenal circular drainage—a complex and invasive open surgical procedure originally implemented and performed in China.

In some cases, SMA Syndrome may occur alongside a serious, life-threatening condition such as cancer or AIDS. Even in these cases, though, treatment of the SMA Syndrome can lead to a reduction in symptoms and an increased quality of life.

Aortic ruptures can be repaired surgically via open aortic surgery or using endovascular therapy (EVAR), regardless of cause, just as non-ruptured aortic aneurysms are repaired. An aortic occlusion balloon can be placed to stabilize the patient and prevent further blood loss prior to the induction of anesthesia.

Sclerotherapy is a treatment for specific veins and vascular malformations in the affected area. It involves the injection of a chemical into the abnormal veins to cause thickening and obstruction of the targeted vessels. Such treatment may allow normal blood flow to resume. It is a non-surgical medical procedure and is not nearly as invasive as debulking. Ultrasound guided foam sclerotherapy is the state of the art new treatment which could potentially close many large vascular malformations.

Compression therapies are finding more use as of the last ten years. The greatest issue with KTS syndrome is that the blood flow and/or lymph flow may be impeded, and will pool in the affected area. This can cause pain, swelling, inflammations, and in some cases, even ulceration and infection. Among older children and adults, compression garments can be used to alleviate almost all of these, and when combined with elevation of the affected area and proper management, can result in a comfortable lifestyle for the patient without any surgery. Compression garments are also used lately after a debulking procedure to maintain the results of the procedure. For early treatment of infants and toddlers with KTS, custom compression garments are impractical because of the rate of growth. When children may benefit from compression therapies, wraps and lymphatic massage may be used. While compression garments or therapy are not appropriate for everyone, they are relatively cheap (compared to surgery), and have few side-effects. Possible side-effects include a slight risk that the fluids may simply be displaced to an undesirable location (e.g., the groin), or that the compression therapy itself further impedes circulation to the affected extremities.

KTS is a complex syndrome, and no single treatment is applicable for everyone. Treatment is decided on a case-by-case basis with the individual's doctors.

At present, many of the symptoms may be treated, but there is no cure for Klippel–Trenaunay syndrome.

Symptoms are usually relieved with radiation therapy within one month of treatment. However, even with treatment, 99% of patients die within two and a half years. This relates to the cancerous causes of SVC that are 90% of the cases. The average age of onset of disease is 54 years of age.

Prevention of PTS begins with prevention of initial and recurrent DVT. For people hospitalized at high-risk of DVT, prevention methods may include early ambulation, use of compression stockings or electrostimulation devices, and/or anticoagulant medications.

Increasingly, catheter-directed thrombolysis has been employed. This is a procedure in which interventional radiology will break up a clot using a variety of methods.

For people who have already had a single DVT event, the best way to prevent a second DVT is appropriate anticoagulation therapy.

A second prevention approach may be weight loss for those who are overweight or obese. Increased weight can put more stress and pressure on leg veins, and can predispose patients to developing PTS.

Treatment consists of painkillers and surgical ablation of the dilated vein. This can be accomplished with open abdominal surgery (laparotomy) or keyhole surgery (laparoscopy). Recently, the first robot-assisted surgery was described.

Another approach to treatment involves catheter-based embolisation, often preceded by phlebography to visualise the vein on X-ray fluoroscopy.

Ovarian vein coil embolisation is an effective and safe treatment for pelvic congestion syndrome and lower limb varices of pelvic origin. Many patients with lower limb varices of pelvic origin respond to local treatment i.e. ultrasound guided sclerotherapy. In those cases, ovarian vein coil embolisation should be considered second line treatment to be used if veins recur in a short time period i.e. 1–3 years. This approach allows further pregnancies to proceed if desired. Coil embolisation is not appropriate if a future pregnancy is possible. This treatment has largely superseded operative options.

Coil embolisation requires exclusion of other pelvic pathology, expertise in endovascular surgery, correct placement of appropriate sized coils in the pelvis and also in the upper left ovarian vein, careful pre- and post-procedure specialist vascular ultrasound imaging, a full discussion of the procedure with the patient i.e. informed consent. Complications, such as coil migration, are rare but reported. Their sequelae are usually minor.

If a Nutcracker compression (see below) is discovered, stenting of the renal vein should be considered before embolization of the ovarian vein. Reducing outflow obstruction should always be the main objective.

Conservative treatment of CVI in the leg involves symptomatic treatment and efforts to prevent the condition from getting worse instead of effecting a cure. This may include

- Manual compression lymphatic massage therapy

- Skin lubrication

- Sequential compression pump

- Ankle pump

- Compression stockings

- Blood pressure medicine

- Frequent periods of rest elevating the legs above the heart level

- Tilting the bed so that the feet are above the heart. This may be achieved by using a 20 cm (7-inch) bed wedge or sleeping in a 6 degree Trendelenburg position. Obese or pregnant patients might be advised by their physicians to forgo the tilted bed.