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A1-G Surg Note Small Bowel > Radiation-Induced Injury to the Small and Large Bowel > Flashcards

Radiation-Induced Injury to the Small and Large Bowel Flashcards

1
Q

What is the most common method of delivering radiation therapy?

A

External beam radiation therapy (EBRT), which uses a linear accelerator to produce ionizing radiation

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2
Q

How does EBRT damage DNA within cells?

A

By interacting with water and releasing free radicals, leading to direct or indirect DNA damage

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3
Q

What are the potential cellular outcomes of DNA damage from EBRT?

A

Mitotic inhibition or cellular apoptosis.

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4
Q

What is brachytherapy

A

A method of radiation delivery involving the placement of a radiation source within the body, often as pellets or beads

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5
Q

What is the “target cell” theory of radiation-induced bowel injury?

A

It describes acute effects targeting bowel epithelium cells and chronic effects targeting cells with slower turnover, such as endothelial cells and fibroblasts.

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6
Q

Which cells are most susceptible to radiation injury and why?

A

Rapidly dividing cells, such as those in the gastrointestinal (GI) tract, because they are the first to be affected

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7
Q

What is a characteristic chronic effect of radiation injury on the bowel?

A

Ischemic injury and fibrosis due to fibroblast reaction to cytokines, growth factors, and chemokines

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8
Q

What pathological changes can chronic radiation injury cause in the bowel?

A

Intestinal atrophy, malabsorption, stricture formation, and vascular damage including telangiectasias and arteriolar constriction.

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9
Q

What are histopathologic features of acute radiation injury to the bowel?

A

Extensive mucosal inflammation
crypt atrophy/abscesses
nuclear atypia with bizarre mitoses
and eosinophilic submucosal infiltration.

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10
Q

What characterizes chronic radiation injury histopathologically?

A

Obliterative enteritis
small-vessel vasculopathy
ulceration
fibrous induration
and superimposed ischemic changes

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11
Q

What can result from arteriolar constriction due to chronic radiation injury?

A

Bowel ischemia and necrosis.

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12
Q

What are common patient-related risk factors for radiation-induced bowel injury?

A

Smoking
diabetes mellitus
hypertension
vascular and collagen disorders
atherosclerosis
coronary artery disease
inflammatory bowel disease
prior intestinal surgery

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13
Q

How can chemotherapy affect the risk of radiation-induced bowel injury?

A

Chemotherapy agents such as
fluoropyrimidines
taxanes
platinum agents
mitomycin C
gemcitabine
methotrexate
actinomycin D
topotecan
doxorubici
can act as radiosensitizers and potentiate radiation effects.

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14
Q

How does body mass index (BMI) influence the risk of radiation-induced bowel injury?

A

Low BMI is associated with a higher risk due to an increased rate of radiation toxicity.

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15
Q

What radiation treatment-related factors increase the risk of radiation-induced bowel injury?

A

Higher radiation dose
longer length of bowel irradiated
fewer dose fractionation
and larger radiation field size.

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16
Q

Why are patients with vascular and collagen disorders at higher risk for radiation-induced bowel injury

A

Because these conditions can impair the vascular supply and structural integrity of the bowel, making it more susceptible to radiation damage.

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17
Q

When can acute radiation-induced bowel injury occur?

A

From the time of radiation treatment up to 6 months after treatment completion.

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18
Q

What is one of the most common symptoms of acute radiation-induced bowel injury?

A

Diarrhea due to mucosal inflammation and damage.

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19
Q

What complication can arise from damage to the mucosal barrier during acute radiation injury?

A

Increased risk for bacterial translocation, leading to bacteremia and sepsis

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20
Q

What are other symptoms of acute radiation-induced bowel injury?

A

Nausea
bloating
cramping
abdominal pain
and GI dysmotility.

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21
Q

What additional symptoms can acute radiation colitis and proctitis present with?

A

Bleeding, mucus discharge, urgency, and tenesmus

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22
Q

When do symptoms of chronic radiation-induced bowel injury typically present?

A

8 to 12 months after treatment, though symptoms can appear up to 30 years later.

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23
Q

What is one of the most common symptoms of chronic radiation-induced bowel injury?

A

Diarrhea, similar to acute radiation injury.

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24
Q

What symptom is common in chronic radiation proctitis?

A

Rectal bleeding due to telangiectasias

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25
Q

What complications can chronic radiation-induced bowel injury lead to?

A

Ulcerations from ischemia, abscesses, fistula formation, stricture formation, and bowel obstruction.

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26
Q

What severe outcomes can result from chronic ischemic changes in the bowel?

A

Full thickness necrosis, fistulae, or free perforation.

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27
Q

How is acute radiation-induced injury to the small intestine, colon, and rectum generally diagnosed?

A

Based on the patient’s presenting symptoms and history.

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28
Q

What diagnostic methods are used for chronic radiation-induced bowel injury?

A

Imaging such as CT scans or MR enterography to evaluate anatomy and assess for strictures, fistulae, or bowel wall thickness abnormalities

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29
Q

What can barium and water-soluble contrast enemas reveal in patients with suspected radiation colitis or proctitis?

A

Shortening, narrowing, lack of distensibility, and absent haustral/mucosal folds of the bowel.

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30
Q

Which imaging methods can be used for further evaluation of fistulae in radiation-induced bowel injury?

A

MRI, fistulograms, cystograms, and pelvic examinations

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31
Q

How is a definitive diagnosis of radiation-induced bowel injury confirmed?

A

Endoscopically with biopsies demonstrating specific histologic features

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32
Q

What type of endoscopy is used for suspected radiation injury to the duodenum?

A

Upper endoscopy

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33
Q

When should capsule endoscopy be considered in evaluating radiation-induced bowel injury?

A

Only if intestinal strictures have been excluded

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34
Q

What is the benefit of lower endoscopy (colonoscopy or sigmoidoscopy) in diagnosing radiation colitis and proctitis?

A

It helps visualize neovascularization with fragile vessels and other signs like pallor and friability

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35
Q

What precaution should be taken when performing rectal biopsies in patients with radiation-induced bowel injury?

A

They should be performed judiciously due to the increased risk of rectal fistula formation.

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36
Q

How are symptoms of acute radiation-induced bowel injury typically managed?

A

Medically, as they are often self-limited

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37
Q

What medications and dietary modifications are used to manage diarrhea in acute radiation-induced bowel injury?

A

Antidiarrheal medications like loperamide
fiber supplements
dietary changes (e.g., lactose-free, low-fat, low-residue, or elemental diet)

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38
Q

What medication can be used if first-line antidiarrheals are ineffective in managing diarrhea from radiation-induced bowel injury?

A

Octreotide.

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39
Q

What treatment options are available for nausea associated with radiation-induced bowel injury?

A

Antiemetics.

40
Q

What additional agents can be used to manage symptoms of radiation-induced bowel injury?

A

Anticholinergics, antispasmodics, bile acid–binding agents like cholestyramine, and antisecretory agents.

41
Q

How can acute radiation proctitis be managed with butyrate enemas?

A

They provide short-chain fatty acids as nutrients for colonocytes, though results for chronic proctitis have been mixed

42
Q

What do the MASCC guidelines recommend for managing chronic proctitis with rectal bleeding?

A

Sucralfate enemas for their protective barrier and epithelial healing properties

43
Q

What are other types of enemas that have been used for radiation proctitis, and what are their outcomes?

A

Mesalamine (5-ASA) enemas
short-chain fatty acid enemas
and steroid enemas
have shown mixed results and require more investigation.

44
Q

What is formalin therapy used for in radiation-induced bowel injury?

A

As a topical treatment for chronic radiation proctitis to chemically cauterize telangiectasias and ulcers

45
Q

How is formalin therapy administered for chronic radiation proctitis?

A

Via irrigation with 4%–10% formalin or direct application using formalin-soaked gauze, followed by formaldehyde washout.

46
Q

What are potential complications of formalin therapy for radiation proctitis?

A

Anal/pelvic pain
stricture
rectal wall necrosis
and fistula formation

47
Q

What are some additional medical treatments that can be considered for radiation-induced bowel injury?

A

Antioxidants (vitamins E and C), probiotics, hyperbaric oxygen, and oral metronidazole

48
Q

What effect has oral metronidazole shown in treating radiation proctitis?

A

It may be associated with decreased bleeding, ulceration, and diarrhea over a 4-week course

49
Q

What endoscopic therapy is the treatment of choice for bleeding in chronic radiation-induced bowel injury?

A

Argon plasma coagulation (APC).

50
Q

What is the success rate of argon plasma coagulation (APC) in stopping bleeding in radiation-induced bowel injury?

A

80% to 90% of cases.

51
Q

Why is APC considered a safe approach for treating bleeding?

A

Because it coagulates tissue at a superficial depth.

52
Q

What improvement, besides stopping bleeding, has been demonstrated after APC treatment?

A

Improvement of bowel function.

53
Q

What precaution should be taken when performing APC in patients with chronic radiation-induced bowel injury?

A

Avoiding the dentate line to prevent anorectal pain

54
Q

What are potential complications of APC?

A

Anorectal pain and abdominal cramping

55
Q

What other endoscopic treatments are alternatives to APC but are rarely performed?

A

Neodymium-doped yttrium aluminum garnet
(Nd;Yag) laser therapy, radiofrequency ablation, and cryotherapy

56
Q

What is a similarity between APC and formalin therapy in the treatment of chronic radiation-induced bowel injury?

A

Both may require multiple treatment sessions.

57
Q

What percentage of patients with chronic radiation-induced bowel injury will require surgical intervention?

A

More than 30%

58
Q

What are indications for surgery in patients with chronic radiation-induced bowel injury?

A

Symptoms not manageable medically or endoscopically, complications such as perforations, fistulae, strictures, obstruction, intractable pain, and incontinence.

59
Q

What is the range of morbidity and mortality rates after surgical intervention for radiation-induced bowel injury?

A

Morbidity: 30% to 65%, Mortality: 6.7% to 25%.

60
Q

Why is surgery in radiation-induced bowel injury considered challenging?

A

Due to a hostile operative environment with friable tissue, extensive adhesions, high risk for bowel injury, and poor healing.

61
Q

What should be included in preoperative planning for patients with radiation-induced bowel injury?

A

Correcting electrolyte derangements, providing enteral nutrition for malnourished patients, and considering individual patient factors in a multidisciplinary setting

62
Q

What surgical options are available for managing radiation-induced bowel injury?

A

Limited bowel resection, bypass/exclusion procedures, stricturoplasty, and fecal diversion

63
Q

What considerations should be made when choosing a surgical incision for patients with chronic radiation injury?

A

Consider impaired wound healing; options include low transverse incisions, lower midline incisions, or a Pfannenstiel incision for thin female patients

64
Q

What is the role of minimally invasive surgery for radiation-induced bowel injury?

A

It is controversial and depends on individual assessment, with diagnostic laparoscopy via open Hasson technique determining feasibility.

65
Q

What are contraindications for a minimally invasive approach in radiation-induced bowel injury surgery?

A

Dense adhesions or pelvic fibrosis.

66
Q

Where should dissection begin in surgery for radiation-induced bowel injury?

A

Proximally, where radiation damage is less severe, moving distally

67
Q

What type of dissection is recommended to prevent bowel injury during surgery for radiation-induced bowel injury?

A

Sharp dissection using Metzenbaum scissors

68
Q

Why should blunt dissection be avoided during surgery for radiation-induced bowel injury?

A

It is associated with a high risk of enterotomy

69
Q

What should be done for patients with extensive, dense adhesions during surgery for radiation-induced bowel injury?

A

Limited adhesiolysis should be performed only in the area of interest and only if the bowel is resectable to reduce the risk of fistula formation and bowel injury

70
Q

What is the surgical challenge associated with pelvic adhesions in radiation-induced bowel injury?

A

Small bowel segments may be adherent in the pelvis, and careful dissection is needed to avoid damaging the presacral veins and managing potential hemorrhage

71
Q

What should a surgeon do if a bowel segment is fibrosed to the sacrum?

A

It may be safer to leave the segment attached and apply diathermy to the mucosal surface.

72
Q

What technique can prevent serosal injuries during the dissection of dense interloop adhesions?

A

Hydrodissection via saline injection.

73
Q

Why is limited bowel resection preferred over bypass/exclusion in surgical management?

A

It is associated with decreased rates of reoperation and increased survival.

74
Q

What should be considered when selecting bowel segments for anastomosis in radiation-induced bowel surgery?

A

Use nonirradiated bowel for anastomosis when possible, as anastomotic leak rates can be as high as 50% between irradiated segments.

75
Q

What are the visual characteristics of grossly irradiated bowel?

A

It can appear pale, mottled, yellowish/gray, or telangiectatic with features of vascular insufficiency, but may sometimes look indistinguishable from normal bowel.

76
Q

Which bowel segments should be avoided for anastomosis in radiation-induced bowel surgery?

A

The cecum and terminal ileum due to their common exposure to severe radiation injury

77
Q

What type of anastomosis is preferred in radiation-induced bowel surgery to avoid staple-line ischemia?

A

Hand-sewn anastomosis.

78
Q

What is the recommended technique for managing the mesentery in radiation-induced bowel surgery?

A

Over-sewing the mesentery with an interlocking heavy #1 chromic suture between clamps, rather than using vessel sealers or the clamp, cut, tie technique

79
Q

When might bypass/exclusion be considered instead of bowel resection in radiation-induced bowel injury?

A

When extensive adhesions and/or pelvic fixation make resection impossible

80
Q

What are the benefits and drawbacks of bypass/exclusion compared to bowel resection?

A

It has a lower risk of bowel or mesenteric injury and lower anastomotic leak rate but increases the risk of blind loop syndrome and fistula formation.

81
Q

What surgical alternative may be used to preserve intestine and avoid TPN dependence in radiation-induced bowel injury?

A

Stricturoplasty.

82
Q

What is a common approach for managing postradiation enteric and pelvic fistulae?

A

Sepsis management, nutritional optimization, and fistula maturation/output optimization.

83
Q

How are higher pelvic fistulae (e.g., rectovaginal, rectourethral) treated surgically?

A

With proctectomy and anastomosis of the colon to the distal nonradiated rectum or anus.

84
Q

When is hand-sewn coloanal anastomosis recommended in radiation-induced bowel injury?

A

Only in younger patients with intact sensation, function, and control

85
Q

What type of tissue is recommended for interposition between the affected organ and anastomosis?

A

Well-vascularized tissue such as omentum or rectus pedicle flap

86
Q

How can lower pelvic fistulae be managed surgically?

A

Through perineal (Kraske) or transsphincteric (York-Mason) approaches.

87
Q

What types of flaps may be used for reconstruction to promote better healing in pelvic fistulae?

A

Gracilis, omentum, rectus, bulbocavernosus, or Martius flaps

88
Q

What is a severe surgical option for cases where pelvic fistulae are extensive?

A

Pelvic exenteration

89
Q

What is the role of fecal diversion in managing radiation-induced bowel injury?

A

It helps manage pain, tenesmus, incontinence, obstruction, and sepsis, especially in non-optimal surgical candidates.

90
Q

Why might loop ileostomies and transverse/descending colostomies be safer than sigmoid colostomies in irradiated pelvis?

A

Due to the difficulty of dissection and higher risk of bowel injury in an irradiated pelvis.

91
Q

What is 3D conformal radiation therapy (3DCRT)?

A

A technique using 3D planning via CT and computer technology to deliver radiation that matches the tumor’s shape, allowing higher doses to the tumor with less impact on normal tissue.

92
Q

What is intensity-modulated radiation therapy (IMRT)?

A

A radiation technology that delivers varying intensities of radiation in a planned field with clear differentiation between malignant and normal tissue.

93
Q

How does brachytherapy help minimize radiation-induced bowel injury?

A

By delivering radiation directly to the tumor or as an adjunct to EBRT to reduce normal tissue exposure.

94
Q

What is proton therapy, and how does it benefit radiation delivery?

A

A new technology used in certain tertiary centers to minimize radiation exposure to surrounding organs and structures

95
Q

What are some positioning and procedural strategies to reduce radiation injury?

A

Prone positioning, use of protective belly boards, and ensuring a full bladder during radiation delivery.

96
Q

What is amifostine, and how is it used in radiation therapy?

A

A prodrug metabolized into a thiol metabolite that acts as a free radical scavenger, potentially preventing symptoms of acute radiation proctitis

97
Q

What operative maneuvers can be considered to minimize radiation injury if radiation is given postoperatively?

A

The use of omental slings and tissue expanders to fill the pelvis

A1-G Surg Note Small Bowel (10 decks)

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