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Various Approaches for CT-guided Percutaneous Biopsy of Deep Pelvic Lesions: Anatomic and Technical Considerations¹

¹ From the Department of Diagnostic Radiology, Section of Vascular and Interventional Radiology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Unit 325, Houston, TX 77030-4009. Recipient of a Certificate of Merit award for an education exhibit at the 2002 RSNA scientific assembly. Received March 14, 2003; revision requested April 14 and received May 13; accepted May 14. Address correspondence to S.G. (e-mail: sgupta@mdanderson.org).

View larger version (179K): [in a new window]   Figure 1a.  (a) Schematic shows an anterior view of the pelvis. civs = common iliac vessels, eivs = external iliac vessels, iivs = internal iliac vessels, ilps = iliopsoas muscles, ur = ureter. On the right side of the pelvis, the piriform muscle (prf) and sciatic nerve (scn) are seen coursing through the greater sciatic foramen. (b) Schematic shows a posterior view of the pelvis. The piriform muscle (prf), sciatic nerve (scn), and superior gluteal vessels (sgvs) are seen coursing through the greater sciatic foramen. ssl = sacrospinous ligament, stl = sacrotuberous ligament.

View larger version (188K): [in a new window]   Figure 1b.  (a) Schematic shows an anterior view of the pelvis. civs = common iliac vessels, eivs = external iliac vessels, iivs = internal iliac vessels, ilps = iliopsoas muscles, ur = ureter. On the right side of the pelvis, the piriform muscle (prf) and sciatic nerve (scn) are seen coursing through the greater sciatic foramen. (b) Schematic shows a posterior view of the pelvis. The piriform muscle (prf), sciatic nerve (scn), and superior gluteal vessels (sgvs) are seen coursing through the greater sciatic foramen. ssl = sacrospinous ligament, stl = sacrotuberous ligament.

View larger version (139K): [in a new window]   Figure 2a.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (132K): [in a new window]   Figure 2b.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (129K): [in a new window]   Figure 2c.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (143K): [in a new window]   Figure 2d.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (118K): [in a new window]   Figure 2e.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (114K): [in a new window]   Figure 2f.  (a) CT scan through the upper pelvis shows the ascending colon (ac), descending colon (dc), and small bowel loops (sbl) occupying the anterior portion of the pelvis. Note the relationship of the common iliac artery (cia), common iliac vein (civ), ureter (ur), and testicular vessels (tvs) to the psoas muscle (ps). il = iliac muscle, ilvs = iliolumbar vessels. (b) On a CT scan through the S2 vertebra, the common iliac vessels have divided into external (eivs) and internal (iivs) iliac vessels. Small bowel loops (sbl) and the sigmoid colon (sgc) occupy a major portion of the pelvis. Note also the left ureter (ur), the inferior epigastric vessels (ievs) posterior to the rectus muscle (rm), the deep circumflex iliac vessels (dcvs) medial to the iliac muscle (il), and the lumbosacral nerve (lsn) anterior to the sacrum. The femoral nerve (fmn) located in the groove between the iliac muscle and the psoas muscle (ps) is usually difficult to identify but is clearly depicted on this image. (c) CT scan through the midpelvis shows the external iliac artery (eia) and external iliac vein (eiv) coursing along the medial aspect of the iliopsoas muscle, the internal iliac vessels (iivs), and the superior gluteal vessels (sgvs) coursing through the upper portion of the greater sciatic foramen. dcvs = deep circumflex iliac vessels, ievs = inferior epigastric vessels, igvs = inferior gluteal vessels, on = obturator nerve, scn = sciatic nerve, sgc = sigmoid colon, tvs = testicular vessels, ub = urinary bladder, ur = ureter. (d) CT scan of a female patient through the midpelvis shows the uterus (ut) and the left adnexa (adn). eivs = external iliac vessels, iivs = internal iliac vessels, lbl = large bowel loop, sbl = small bowel loops, ur = ureter. (e) CT scan through the cephalic portion of the greater sciatic foramen (gsf) shows the obturator internus (oi) and piriform (prf) muscles and the sciatic nerve (scn) close to the ischium, as well as the external iliac vessels (eivs), inferior epigastric vessels (ievs), inferior gluteal vessels (igvs), internal pudendal vessels (ipvs), obturator nerve (on), rectum (re), urinary bladder (ub), ureter (ur), and vas deferens (vd). (f) CT scan through the caudal portion of the sciatic foramen shows the urinary bladder (ub), rectum (re), sacrospinous ligament (ssl), seminal vesicles (sv), inferior gluteal vessels (igvs), and external iliac vessels (eivs). Note the cranial portion of the periprostatic venous plexus (pvp) located medial to the obturator internus muscle (oi).

View larger version (95K): [in a new window]   Figure 3a.  Anterior transabdominal approach. (a) CT scan shows a hypoattenuating mass (m) located anterior to the psoas muscle (ps) and iliac vessels (arrow). Note the potential access point between bowel loops (arrowheads). (b) CT scan clearly depicts an 18-gauge needle that was advanced between the bowel loops (arrowheads) for biopsy of the mass (m). Arrow indicates the iliac vessels. ps = psoas muscle.

View larger version (99K): [in a new window]   Figure 3b.  Anterior transabdominal approach. (a) CT scan shows a hypoattenuating mass (m) located anterior to the psoas muscle (ps) and iliac vessels (arrow). Note the potential access point between bowel loops (arrowheads). (b) CT scan clearly depicts an 18-gauge needle that was advanced between the bowel loops (arrowheads) for biopsy of the mass (m). Arrow indicates the iliac vessels. ps = psoas muscle.

View larger version (126K): [in a new window]   Figure 4.  Inadvertent bowel transgression. CT scan obtained during biopsy (anterior abdominal approach) of an external iliac lymph node (n) shows a 22-gauge needle transgressing a small bowel loop (arrow). Note the external iliac vessels (arrrowhead) located just anterolateral to the node.

View larger version (157K): [in a new window]   Figure 5a.  Modified lateral transabdominal approach. (a) Supine CT scan shows the large bowel (lb) and small bowel (sb) anterior to a node (n) located posterolateral to the common iliac vessels (arrow). (b) CT scan obtained with the patient in the left lateral decubitus position demonstrates a newly created window lateral to the large bowel (lb). n = common iliac node. (c) CT scan obtained during the injection of saline solution (arrows) through an 18-gauge needle shows further displacement of the large bowel (lb). n = common iliac node. (d) CT scan shows a 22-gauge needle that was advanced through the guide needle for biopsy of the node (n). lb = large bowel.

View larger version (149K): [in a new window]   Figure 5b.  Modified lateral transabdominal approach. (a) Supine CT scan shows the large bowel (lb) and small bowel (sb) anterior to a node (n) located posterolateral to the common iliac vessels (arrow). (b) CT scan obtained with the patient in the left lateral decubitus position demonstrates a newly created window lateral to the large bowel (lb). n = common iliac node. (c) CT scan obtained during the injection of saline solution (arrows) through an 18-gauge needle shows further displacement of the large bowel (lb). n = common iliac node. (d) CT scan shows a 22-gauge needle that was advanced through the guide needle for biopsy of the node (n). lb = large bowel.

View larger version (146K): [in a new window]   Figure 5c.  Modified lateral transabdominal approach. (a) Supine CT scan shows the large bowel (lb) and small bowel (sb) anterior to a node (n) located posterolateral to the common iliac vessels (arrow). (b) CT scan obtained with the patient in the left lateral decubitus position demonstrates a newly created window lateral to the large bowel (lb). n = common iliac node. (c) CT scan obtained during the injection of saline solution (arrows) through an 18-gauge needle shows further displacement of the large bowel (lb). n = common iliac node. (d) CT scan shows a 22-gauge needle that was advanced through the guide needle for biopsy of the node (n). lb = large bowel.

View larger version (143K): [in a new window]   Figure 5d.  Modified lateral transabdominal approach. (a) Supine CT scan shows the large bowel (lb) and small bowel (sb) anterior to a node (n) located posterolateral to the common iliac vessels (arrow). (b) CT scan obtained with the patient in the left lateral decubitus position demonstrates a newly created window lateral to the large bowel (lb). n = common iliac node. (c) CT scan obtained during the injection of saline solution (arrows) through an 18-gauge needle shows further displacement of the large bowel (lb). n = common iliac node. (d) CT scan shows a 22-gauge needle that was advanced through the guide needle for biopsy of the node (n). lb = large bowel.

View larger version (123K): [in a new window]   Figure 6a.  Modified lateral transabdominal approach. (a) Supine CT scan shows a soft-tissue mass (m) posterior to the urinary bladder (ub) and bowel loops (arrows). (b) CT scan obtained with the patient in the decubitus position shows a straight needle (arrowhead) that was advanced coaxially through a guide needle (arrow) but did not reach the center of the mass (m). ub = urinary bladder. (c) CT scan shows a curved 22-gauge needle (arrowhead) that was advanced coaxially through the guide needle to circumvent the urinary bladder (ub), thereby allowing safe biopsy of the mass (m).

View larger version (130K): [in a new window]   Figure 6b.  Modified lateral transabdominal approach. (a) Supine CT scan shows a soft-tissue mass (m) posterior to the urinary bladder (ub) and bowel loops (arrows). (b) CT scan obtained with the patient in the decubitus position shows a straight needle (arrowhead) that was advanced coaxially through a guide needle (arrow) but did not reach the center of the mass (m). ub = urinary bladder. (c) CT scan shows a curved 22-gauge needle (arrowhead) that was advanced coaxially through the guide needle to circumvent the urinary bladder (ub), thereby allowing safe biopsy of the mass (m).

View larger version (130K): [in a new window]   Figure 6c.  Modified lateral transabdominal approach. (a) Supine CT scan shows a soft-tissue mass (m) posterior to the urinary bladder (ub) and bowel loops (arrows). (b) CT scan obtained with the patient in the decubitus position shows a straight needle (arrowhead) that was advanced coaxially through a guide needle (arrow) but did not reach the center of the mass (m). ub = urinary bladder. (c) CT scan shows a curved 22-gauge needle (arrowhead) that was advanced coaxially through the guide needle to circumvent the urinary bladder (ub), thereby allowing safe biopsy of the mass (m).

View larger version (146K): [in a new window]   Figure 7.  Transgluteal approach. CT scan shows a needle that passes through the sacrospinous ligament (arrow) close to the sacrum and posterior to the inferior gluteal vessels (arrowhead) for biopsy of a presacral mass (m).

View larger version (119K): [in a new window]   Figure 8.  Transgluteal approach. CT scan shows a needle that traverses the sacrospinous ligament (arrowheads) and the inferior portion of the piriform muscle (straight arrow) for biopsy of a perirectal nodule (curved arrow).

View larger version (141K): [in a new window]   Figure 9.  Transgluteal approach. CT scan shows a curved inner needle (arrowhead) that was advanced coaxially through a guide needle for biopsy of an internal iliac lymph node (curved arrow) posterior to the urinary bladder. The needles were inserted through the sacrospinous ligament and between the rectum (re) and the inferior gluteal vessels (straight arrow).

View larger version (112K): [in a new window]   Figure 10.  Transgluteal approach. Prone CT scan shows a needle (arrowhead) that traverses the piriform muscle (prf) adjacent to the sacrum (sa) and medial to the internal iliac vessel branches (arrows) for biopsy of an adnexal mass (m).

View larger version (103K): [in a new window]   Figure 11a.  Anterolateral approach. (a) CT scan shows an obturator lymph node (arrow). Note how the urinary bladder (ub), sigmoid colon (sgc), and external iliac vessels (arrowhead) obstruct an anterior approach. A transgluteal approach was obstructed by the sacrum. (b) CT scan shows a needle that was advanced through the iliopsoas muscle medial to the external iliac vessels (arrowhead) for biopsy of the node (arrow).

View larger version (107K): [in a new window]   Figure 11b.  Anterolateral approach. (a) CT scan shows an obturator lymph node (arrow). Note how the urinary bladder (ub), sigmoid colon (sgc), and external iliac vessels (arrowhead) obstruct an anterior approach. A transgluteal approach was obstructed by the sacrum. (b) CT scan shows a needle that was advanced through the iliopsoas muscle medial to the external iliac vessels (arrowhead) for biopsy of the node (arrow).

View larger version (102K): [in a new window]   Figure 12a.  Anterolateral approach. (a) CT scan shows an obturator node (straight arrow). Note how the external (curved arrow) and internal (arrowhead) iliac vessels, rectum (re), and urinary bladder (ub) preclude direct access. (b) CT scan shows a needle (arrowhead) that was advanced through the iliopsoas muscle for biopsy of the node (arrow).

View larger version (111K): [in a new window]   Figure 12b.  Anterolateral approach. (a) CT scan shows an obturator node (straight arrow). Note how the external (curved arrow) and internal (arrowhead) iliac vessels, rectum (re), and urinary bladder (ub) preclude direct access. (b) CT scan shows a needle (arrowhead) that was advanced through the iliopsoas muscle for biopsy of the node (arrow).

View larger version (137K): [in a new window]   Figure 13.  Anterolateral approach. CT scan shows a needle that was advanced through the iliopsoas muscle for biopsy of an external iliac node (arrow) located anterior to the external iliac vessels (curved arrow). A direct anterior approach was obstructed by bowel loops (arrowheads).

View larger version (106K): [in a new window]   Figure 14a.  Anterolateral approach. (a) Contrast-enhanced CT scan shows a soft-tissue mass (m) engulfing the iliac vessels (arrows). The presence of bowel loops (b) precluded a direct anterior approach. The straight line at the upper left represents the planned needle trajectory. (b) CT scan shows a needle (arrow) that passes lateral to the bowel (b) and through the iliopsoas muscle for biopsy of the mass (m).

View larger version (107K): [in a new window]   Figure 14b.  Anterolateral approach. (a) Contrast-enhanced CT scan shows a soft-tissue mass (m) engulfing the iliac vessels (arrows). The presence of bowel loops (b) precluded a direct anterior approach. The straight line at the upper left represents the planned needle trajectory. (b) CT scan shows a needle (arrow) that passes lateral to the bowel (b) and through the iliopsoas muscle for biopsy of the mass (m).

View larger version (110K): [in a new window]   Figure 15a.  Modified anterolateral approach. (a) CT scan shows a loculated fluid collection (fl) adjacent to the external iliac vessels (arrow). A direct approach was obstructed by bowel loops (b). (b) CT scan shows a curved 22-gauge needle (straight arrow) that has been advanced through a straight 18-gauge guide needle (curved arrow) and passes anterior to the iliac vessels (arrowhead) and into the fluid collection (fl).

View larger version (113K): [in a new window]   Figure 15b.  Modified anterolateral approach. (a) CT scan shows a loculated fluid collection (fl) adjacent to the external iliac vessels (arrow). A direct approach was obstructed by bowel loops (b). (b) CT scan shows a curved 22-gauge needle (straight arrow) that has been advanced through a straight 18-gauge guide needle (curved arrow) and passes anterior to the iliac vessels (arrowhead) and into the fluid collection (fl).

View larger version (98K): [in a new window]   Figure 16a.  Anterolateral approach. (a) CT scan shows how a direct anterior or posterior approach to an adnexal mass (m) is obstructed by bowel (b) and by the external (arrow) and internal (arrowheads) iliac vessels. (b) CT scan shows a needle that has been advanced through the iliopsoas muscle and passes medial to the iliac vessels (arrow) for biopsy of the mass (m).

View larger version (101K): [in a new window]   Figure 16b.  Anterolateral approach. (a) CT scan shows how a direct anterior or posterior approach to an adnexal mass (m) is obstructed by bowel (b) and by the external (arrow) and internal (arrowheads) iliac vessels. (b) CT scan shows a needle that has been advanced through the iliopsoas muscle and passes medial to the iliac vessels (arrow) for biopsy of the mass (m).

View larger version (100K): [in a new window]   Figure 17.  Transsacral approach. CT scan shows the use of transsacral access for biopsy of a presacral lesion (m) located above the level of the sciatic foramen, which precludes a transgluteal approach. An anterior approach was obstructed by bowel loops. The needle has been advanced through the sacrum lateral to the sacral foramen (arrow).

View larger version (114K): [in a new window]   Figure 18a.  Transsacral approach. (a) Supine CT scan shows a soft-tissue mass (m) located posterior to the urinary bladder (ub) and sigmoid colon (sgc) and anterior to the rectum (re). Branches of the internal iliac vessels (arrow) precluded a transgluteal approach. (b) Prone CT scan shows that a transsacral approach with a curved inner needle (arrowhead) allowed safe access to the mass (m).

View larger version (108K): [in a new window]   Figure 18b.  Transsacral approach. (a) Supine CT scan shows a soft-tissue mass (m) located posterior to the urinary bladder (ub) and sigmoid colon (sgc) and anterior to the rectum (re). Branches of the internal iliac vessels (arrow) precluded a transgluteal approach. (b) Prone CT scan shows that a transsacral approach with a curved inner needle (arrowhead) allowed safe access to the mass (m).

View larger version (106K): [in a new window]   Figure 19.  Transsacral approach. CT scan shows transsacral access to a pelvic mass (m) through an area of lytic disease involvement of the sacrum (arrow). Note the inferior gluteal vessels (arrowhead) lateral to the needle.

View larger version (84K): [in a new window]   Figure 20a.  Transiliac approach. (a) On a supine CT scan, loops of small bowel (sb) and large bowel (lb) obstruct a straight path to a common iliac node (n). Note the iliac vessels (arrow) located posterior to the node. (b) Prone CT scan shows an 18-gauge needle that was advanced through the iliac bone (arrowhead) and the iliac (il) and psoas (ps) muscles for biopsy of the node.

View larger version (98K): [in a new window]   Figure 20b.  Transiliac approach. (a) On a supine CT scan, loops of small bowel (sb) and large bowel (lb) obstruct a straight path to a common iliac node (n). Note the iliac vessels (arrow) located posterior to the node. (b) Prone CT scan shows an 18-gauge needle that was advanced through the iliac bone (arrowhead) and the iliac (il) and psoas (ps) muscles for biopsy of the node.

View larger version (130K): [in a new window]   Figure 21a.  Transiliac approach. (a) CT scan shows a soft-tissue mass (m) along the lateral pelvic sidewall and adjacent to the external iliac vessels (arrows). The presence of bowel loops (b) precluded a direct approach. (b) CT scan obtained with the patient in the decubitus position shows a transiliac approach, with the needle traversing the iliac bone (arrow) for biopsy of the mass (m).

View larger version (150K): [in a new window]   Figure 21b.  Transiliac approach. (a) CT scan shows a soft-tissue mass (m) along the lateral pelvic sidewall and adjacent to the external iliac vessels (arrows). The presence of bowel loops (b) precluded a direct approach. (b) CT scan obtained with the patient in the decubitus position shows a transiliac approach, with the needle traversing the iliac bone (arrow) for biopsy of the mass (m).